Why do you want to do this, if you don't mind me asking?
Anyway, here it is:
<form onsubmit='passSelectValue(this.sel)' [other attributes]>
<select id='sel'>
<option value='one'>one</option>
<option value='two'>two</option>
<option value='three'>three</option>
</select>
<input type='hidden' name='something' id='hiddenField'/>
</form>
<script type='text/javascript'>
function passSelectValues(handle)
{
document.getElementById('hiddenField').value = handle.options[handle.selectedIndex].value;
}
</script>
If you want to get the text of the selected option instead of the value, use .text instead of .value.
HTH,
Snib
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