Salve ho un form di queto form i controlli funzionano dappertutto , solo un controllo multiplo da problemi , questa la parte del form :

codice:
 <select name="costopasto"  id="costopasto" onblur="check_notnull('costopasto')">
			 	<option value="">Seleziona....</option>
			 	<option value="1">1</option>
			 	<option value="2">2</option>
				<option value="3">3</option>
		   		<option value="4">4</option>
			 	<option value="5">5</option>
				<option value="6">6</option>
		  		<option value="7">7</option>
				<option value="8">8</option>
				<option value="9">9</option>
				<option value="10">10</option>
				<option value="11">11</option>
			 	<option value="12">12</option>
				<option value="13">13</option>
		   		<option value="14">14</option>
			 	<option value="15">15</option>
				<option value="16">16</option>
		  		<option value="17">17</option>
				<option value="18">18</option>
				<option value="19">19</option>
				<option value="20">20</option>
				<option value="21">21</option>
			 	<option value="22">22</option>
				<option value="23">23</option>
		   		<option value="24">24</option>
			 	<option value="25">25</option>
				<option value="26">26</option>
		  		<option value="27">27</option>
				<option value="28">28</option>
				<option value="29">29</option>
				<option value="30">30</option>
				<option value="21">21</option>
				<option value="22">22</option>
				<option value="23">23</option>
				<option value="24">24</option>
				<option value="25">25</option>
				<option value="26">26</option>
				<option value="27">27</option>
				<option value="28">28</option>
				<option value="29">29</option>
				<option value="30">30</option>
				<option value="31">31</option>
				<option value="32">32</option>
				<option value="33">33</option>
				<option value="34">34</option>
				<option value="35">35</option>
				<option value="36">36</option>
				<option value="37">37</option>
				<option value="38">38</option>
				<option value="39">39</option>
				<option value="40">40</option>
				<option value="41">41</option>
				<option value="42">42</option>
				<option value="43">43</option>
				<option value="44">44</option>
				<option value="45">45</option>
				<option value="46">46</option>
				<option value="47">47</option>
				<option value="48">48</option>
				<option value="49">49</option>
				<option value="50">50</option>
				<option value="51">51</option>
				<option value="52">52</option>
				<option value="53">53</option>
				<option value="54">54</option>
				<option value="55">55</option>
				<option value="56">56</option>
				<option value="57">57</option>
				<option value="58">58</option>
				<option value="59">59</option>
				<option value="60">60</option>
				<option value="61">61</option>
				<option value="62">62</option>
				<option value="63">63</option>
				<option value="64">64</option>
				<option value="65">65</option>
				<option value="66">66</option>
				<option value="67">67</option>
				<option value="68">68</option>
				<option value="69">69</option>
				<option value="70">70</option>
				<option value="71">71</option>
				<option value="72">72</option>
				<option value="73">73</option>
				<option value="74">74</option>
				<option value="75">75</option>
				<option value="76">76</option>
				<option value="77">77</option>
				<option value="78">78</option>
				<option value="79">79</option>
				<option value="80">80</option>
				<option value="81">81</option>
				<option value="82">82</option>
				<option value="83">83</option>
				<option value="84">84</option>
				<option value="85">85</option>
				<option value="86">86</option>
				<option value="87">87</option>
				<option value="88">88</option>
				<option value="89">89</option>
				<option value="90">90</option>
				<option value="91">91</option>
				<option value="92">92</option>
				<option value="93">93</option>
				<option value="94">94</option>
				<option value="95">95</option>
				<option value="96">96</option>
				<option value="97">97</option>
				<option value="98">98</option>
				<option value="99">99</option>
				<option value="100">100</option>
			</select>


			<br />


	




	
			<h4 class="h4offerta  ">Prezzo ridotto a persona in &euro;</h4><div id="costoridotto1"></div>
			 <select name="costoridotto" id="costoridotto"  onblur="controllopasti()" onclick="controllopasti()">
			 	<option value="">Seleziona...</option>
			  	<option value="0.5">Nessuna Riduzione</option>
			 	<option value="0">Gratuito</option>
			 	<option value="2">2</option>
				<option value="3">3</option>
		   		<option value="4">4</option>
			 	<option value="5">5</option>
				<option value="6">6</option>
		  		<option value="7">7</option>
				<option value="8">8</option>
				<option value="9">9</option>
				<option value="10">10</option>
				<option value="11">11</option>
			 	<option value="12">12</option>
				<option value="13">13</option>
		   		<option value="14">14</option>
			 	<option value="15">15</option>
				<option value="16">16</option>
		  		<option value="17">17</option>
				<option value="18">18</option>
				<option value="19">19</option>
				<option value="20">20</option>
				<option value="21">21</option>
				<option value="22">22</option>
				<option value="23">23</option>
				<option value="24">24</option>
				<option value="25">25</option>
				<option value="26">26</option>
				<option value="27">27</option>
				<option value="28">28</option>
				<option value="29">29</option>
				<option value="30">30</option>
				<option value="31">31</option>
				<option value="32">32</option>
				<option value="33">33</option>
				<option value="34">34</option>
				<option value="35">35</option>
				<option value="36">36</option>
				<option value="37">37</option>
				<option value="38">38</option>
				<option value="39">39</option>
				<option value="40">40</option>
				<option value="41">41</option>
				<option value="42">42</option>
				<option value="43">43</option>
				<option value="44">44</option>
				<option value="45">45</option>
				<option value="46">46</option>
				<option value="47">47</option>
				<option value="48">48</option>
				<option value="49">49</option>
				<option value="50">50</option>
				
			</select>


				<br />
	


			
		


		
			<h4 >Motivo della riduzione(convenzioni,bambini,ecc)</h4><div id="riduzione1"></div>
			<div><input type="text" name="riduzione" maxlength="250" id='riduzio' style="width: 95%;" onblur="check_notnull(this)"></div>
Il controllo su questi campi è :

codice:
var controllopasti=function(){


	var prezzo        = eval("document.offer1.costopasto.value;");
	var prezzoridotto = eval("document.offer1.costoridotto.value;");
	var motivazione   =       document.offer1.riduzione.value;
	


	if (prezzoridotto!='') {
		if(prezzo<=prezzoridotto){


			 document.getElementById('costoridotto1').innerHTML = '<img src="img/no.png"> Prezzo ridotto deve essere minore del prezzo';
		     controllopasto=0;	
		}
		else if((prezzoridotto!=0 && prezzoridotto!=0.5) && motivazione==''){


			 document.getElementById('costoridotto1').innerHTML = '<img src="img/no.png"> Inserire motivazione e riseleziona prezzo ridotto';
		     controllopasto=0;	


		}
		else{
				
		   	document.getElementById('costoridotto1').innerHTML = '<img src="img/si.png">';
			controllopasto=1;
						
		}
	}
	else{


			 document.getElementById('costoridotto1').innerHTML = '<img src="img/no.png"> Seleziona riduzione';
		     controllopasto=0;	
	}
	
		console.log('prezzo'+prezzo);
	console.log('motivazione'+motivazione);


	console.log('prezzoridotto'+prezzoridotto);
	check_allok();


}
a volte non controlla bene i costi e da errore anche se nella console vedo il prezzo ridotto più basso.

Mentre se selezionoil prezzo ridotto , mi fa inserire la motivazione la inserisco e cambio il prezzo non ho + il controllo della differenza di prezzo .
Sapete perchè ?