select

[Mich_]

Non so se ho capito. Vedi se e` questo:

<form ...>
<select ... onchange="if(this.options[this.selectedIndex].value=='altro') this.form.altro.disabled=false;">
<option value="...">...</option>
<option value="...">...</option>
<option value="...">...</option>
<option value="altro">ALTRO (specificare --&amp;gt;)</option>
</select>
<input type="text" name="altro" disabled="true">
...
</form>