oops, i think i misunderstood you... D'oh!
here are a few things to try:
<META HTTP-EQUIV="Pragma" CONTENT="no-cache">
<META HTTP-EQUIV="Pragma-directive" CONTENT="no-cache">
<META HTTP-EQUIV="cache-directive" CONTENT="no-cache">
<META HTTP-EQUIV="Cache-Control" CONTENT="no-cache, must-validate">
<META http-equiv="Cache-Control" content="must-revalidate">