Yeah precisely! The Z-index of a SELECT is more than that of layers. A change doesn't effect too!
So, here's what i opted to handle the problem. Its wat Scout suggested. The code is simple:
Code:
<script language=JavaScript>
var flgHide
function HideCombo()
{
 if (event.clientX > 333 && event.clientX < 780 && event.clientY>0 && event.clientY<20)
	flgHide=true
 if (flgHide==true) 
 {
  if (event.clientX > 333 && event.clientY>0 && event.clientX < 780 && event.clientY<78)
	document.ProjForm.MFProjCombo.style.visibility="hidden"
  else
  {
	document.ProjForm.MFProjCombo.style.visibility="visible"
	flgHide=false
  }
 }
 else
	document.ProjForm.MFProjCombo.style.visibility="visible"
}
</script>
<body onMouseOver="HideCombo()">
The co-ord values that are hard-coded in the above code were manually found using the mouseover event to suit my menu/combo locations. U might have to change them to suit urs. As given above, use the clientX,clientY attributes to find the window co-ords.
Hope this helps.

-Jemima.