Deshabilitar controles con Ajax

[Nefertiter]

creo seria algo asi

<script>

Deshabilitar ($id){
document.getElementById($id).disabled;
}

</script>

<input name="text_1" type="text" id="text_1" size="37">
<input name="text_2" type="text" id="text_2" size="37">

<select name="test" onchange="Deshabilitar(this.selectedIndex)">
<option value="text_1">Text 1</option>
<option value="text_2">Text 2</option>
</select>