You can use a mixture of scripts in your web page that run both on the server and on the client simultaneously. Of course, you'll need separate <script></script> element pairs for the server-side scripts and for the scripts you want to have run on the client's computer. I'm sure the little code below is far from what you'll actually need, but maybe it will help.
<head>
<title>
Snazzy Title
</title>
</head>
<body>
<form name="frmTest">
<input name="txtSomeData" type="text" size=6 />
<input name="cmdSubmit" type="submit" value="Submit" />
<!-- Omittion of the RUNAT="server" attribute below
causes the script to be ran on the client (which
is what we want: we want to validate something on
the page before it is sent off to the server.) -->
<script language="VBScript">
<!--
Sub cmdSubmit_onClick()
x = document.frmTest.txtSomeData.value
If Not(IsNumeric(x)) Then
MsgBox "Please enter numeric characters only."
Exit Sub
Else
MsgBox "The form has been validated" & _
" and will be sent to the server."
' Some other code can go here, such as your code to
' submit the form.
End If
End Sub
-->
</script>
<script language="VBScript" runat="server">
<!--
' Whatever code you want or need could go here...
-->
</script>
</form>
</body>
</html>
