intendo:

<script>
function sendform(idform)
{
if(document.form[idform].fQTA.value != "")
document.form[idform].submit()
else
alert('vuoto')
}
</script>
<form name="form<%=rsDBRecord("IDRecord")%>" id="form<%=rsDBRecord("IDRecord")%>" method="post">

<input name="fQTA" type="text" id="fQTA" value="<%=rsDBRecord("QTA")%>" size="2" onBlur="javascript:sendform('<%=rsDBRecord("IDReco rd")%>')" >
</form>