onSubmit="submitonce(this)"
<script language="javascript">
function submitonce(theform){
if (document.all||document.getElementById){
for (i=0;i<theform.length;i++){
var tempobj=theform.elements
if(tempobj.type.toLowerCase()=="submit")
tempobj.disabled=true
}
}
}
</script>
document.fHtmlEditor.Submit.disabled=true;