Ho uno script che mi fa la somma dei prodotti che ordino e nella casella del totale mi restituisce l'errore NaN, a cosa è dovuto?
Metto qui parte del codice della pagina relativo alla casella totale:


codice:
Totale Ordine
          <input name="TotaleOrdine" type="text" id="TotaleOrdine" value="0" size="8" readonly="yes">
          
 </td> 
      </tr> 
    </table> 
  </div> 
  <div align="center"> 
    <Script Language="JavaScript">
<% If MyMaths1 <> ""  Then %>
function Totale_Categoria_1(){
	document.MyOrder.TotaleCat1.value = <% = MyMaths1 %>
}

<% 
End If

If MyMaths2 <> ""  Then 
%>

function Totale_Categoria_2(){
	document.MyOrder.TotaleCat2.value = <% = MyMaths2 %>
}

<% 
End If

If MyMaths3 <> ""  Then 
%>

function Totale_Categoria_3(){
	document.MyOrder.TotaleCat3.value = <% = MyMaths3 %>
}

<% 
End If

If MyMaths4 <> ""  Then 
%>

function Totale_Categoria_4(){
	document.MyOrder.TotaleCat4.value = <% = MyMaths4 %>
}

<% 
End If

If MyMaths5 <> ""  Then 
%>

function Totale_Categoria_5(){
	document.MyOrder.TotaleCat5.value = <% = MyMaths5 %>
}

<% 
End If

If MyMaths6 <> ""  Then 
%>

function Totale_Categoria_6(){
	document.MyOrder.TotaleCat6.value = <% = MyMaths6 %>
}

<% 
End If

If MyMaths7 <> ""  Then 
%>

function Totale_Categoria_7(){
	document.MyOrder.TotaleCat7.value = <% = MyMaths7 %>
}

<% 
End If

If MyMaths8 <> ""  Then 
%>

function Totale_Categoria_8(){
	document.MyOrder.TotaleCat8.value = <% = MyMaths8 %>
}

<% 
End If

If MyMaths9 <> ""  Then 
%>

function Totale_Categoria_9(){
	document.MyOrder.TotaleCat9.value = <% = MyMaths9 %>
}

<% 
End If

If MyMaths10 <> ""  Then 
%>

function Totale_Categoria_10(){
	document.MyOrder.TotaleCat10.value = <% = MyMaths10 %>
}

<% 
End If

If MyMaths11 <> ""  Then 
%>

function Totale_Categoria_11(){
	document.MyOrder.TotaleCat11.value = <% = MyMaths11 %>
}

<% 
End If

If MyMaths12 <> ""  Then 
%>

function Totale_Categoria_12(){
	document.MyOrder.TotaleCat12.value = <% = MyMaths12 %>
}

<% 
End If

If MyMaths13 <> ""  Then 
%>

function Totale_Categoria_13(){
	document.MyOrder.TotaleCat13.value = <% = MyMaths13 %>
}

<% 
End If

If MyMaths14 <> ""  Then 
%>

function Totale_Categoria_14(){
	document.MyOrder.TotaleCat14.value = <% = MyMaths14 %>
}

<% 
End If

If MyMaths15 <> ""  Then 
%>

function Totale_Categoria_15(){
	document.MyOrder.TotaleCat15.value = <% = MyMaths15 %>
}

<% 
End If

If MyMaths16 <> ""  Then 
%>

function Totale_Categoria_16(){
	document.MyOrder.TotaleCat16.value = <% = MyMaths16 %>
}

<% 
End If

If MyMaths17 <> ""  Then 
%>

function Totale_Categoria_17(){
	document.MyOrder.TotaleCat17.value = <% = MyMaths17 %>
}

<% 
End If

If MyMaths18 <> ""  Then 
%>

function Totale_Categoria_18(){
	document.MyOrder.TotaleCat18.value = <% = MyMaths18 %>
}

<% 
End If

If MyMaths19 <> ""  Then 
%>

function Totale_Categoria_19(){
	document.MyOrder.TotaleCat19.value = <% = MyMaths19 %>
}

<% 
End If

If MyMaths20 <> ""  Then 
%>

function Totale_Categoria_20(){
	document.MyOrder.TotaleCat20.value = <% = MyMaths20 %>
}

<% End IF %>


function Totale_Ordine(){
	document.MyOrder.TotaleOrdine.value = <% If MyMaths1 <> "" Then Response.Write(MyMaths1) %> <% If MyMaths2 <> "" Then Response.Write(" + " & MyMaths2) %> <% If MyMaths3 <> "" Then Response.Write(" + " & MyMaths3) %> <% If MyMaths4 <> "" Then Response.Write(" + " & MyMaths4) %> <% If MyMaths5 <> "" Then Response.Write(" + " & MyMaths5) %> <% If MyMaths6 <> "" Then Response.Write(" + " & MyMaths6) %> <% If MyMaths7 <> "" Then Response.Write(" + " & MyMaths7) %> <% If MyMaths8 <> "" Then Response.Write(" + " & MyMaths8) %> <% If MyMaths9 <> "" Then Response.Write(" + " & MyMaths9) %> <% If MyMaths10 <> "" Then Response.Write(" + " & MyMaths10) %> <% If MyMaths11 <> "" Then Response.Write(" + " & MyMaths11) %> <% If MyMaths12 <> "" Then Response.Write(" + " & MyMaths12) %> <% If MyMaths13 <> "" Then Response.Write(" + " & MyMaths13) %> <% If MyMaths14 <> "" Then Response.Write(" + " & MyMaths14) %> <% If MyMaths15 <> "" Then Response.Write(" + " & MyMaths15) %> <% If MyMaths16 <> "" Then Response.Write(" + " & MyMaths16) %> <% If MyMaths17 <> "" Then Response.Write(" + " & MyMaths17) %> <% If MyMaths18 <> "" Then Response.Write(" + " & MyMaths18) %> <% If MyMaths19 <> "" Then Response.Write(" + " & MyMaths19) %> <% If MyMaths20 <> "" Then Response.Write(" + " & MyMaths20) %>

	if (document.MyOrder.TotaleOrdine.value != 0){
		document.MyOrder.Ordine.disabled = false
	}
}

  </script>