the .value of a <select> is the currently selected item, lust like an input.
if you submit the form, it should have the selected values in it, just like a hidden input would.
still, for the sake of illustration, here a simplified example of what you are trying to do:
<form onsubmit=' x.value=sel.value; alert(x.value) '>
<select id=sel name=sel>
<option> 1 </option>
<option> 2 </option>
<option value='three'> 3 </option>
<input id=x name=x value='-1'>