This sounds like a good time for JavaScript. Put this in <head>:
<script language="JavaScript">
<!--
function loading()
{
if (document.getElementById)
{ // DOM3 = IE5, NS6
document.getElementById('hidepage').style.visibility = 'hidden';
}
else
{
if (document.layers)
{ // Netscape 4
document.hidepage.visibility = 'hidden';
}
else
{ // IE 4
document.all.hidepage.style.visibility = 'hidden';
}
}
}
//-->
</script>
And then put this in <body>:
<span id="hidepage" style="position: absolute; left: 0px; top: 0px">
<table width="100%" height="100%">
<tr>
<td>Your search is being processed - Please wait</td>
</tr>
</table>
</span>
And make the <body>-tag look something like this:
<body onload="loading()">