<script>
function sf(f) {
for (i=0; i<f.form.selField.length; i++)
if (f.form.selField.options[i].value == f.value) {
f.form.selField.options[i].selected = true;
break;
}
}
</script>
<select name="selField">
option
<input type="text" onChange="sf(this)">