Onfocus For A <select>

I'm fairly new to this and my code is as follows...

<script language="JavaScript>
var oldValue

function focusElement(theElement) {
oldValue = theElement.value;
return;
}
</script>

Then in the HTML, I have

<select size="1" id="ConfCommentSELECT" name="ConfCommentSELECT"
onfocus="return focusPrecedence(this);">
<option value="0"> - </option>
<option value="1">1</option>
<option value="2">2</option>
</select>

The <select> is with a <form><tr><td>, but I don't see how that would make a
difference. I started using the onchange="return blah-blah-blah(this);" and
that worked so I copied that to the onfocus. What I want to do is to
remember the value of the contents of the <select> before the user changes
it, and compare it to the new value.