Auto Form Submit

Hi guys,

I have the following

<form name="formpurchase" id="formpurchase"
method=postaction="https://site.cgi";>
<input type=hidden name="MerchantNumber" value="<%=MerchantNumber
%>">
<input type=hidden name="ReturnURL" value="<%=retURL %>">
<input type=hidden name="Products" value="<%=Products %>">

<input type=submit value="Continue" name="submit">
</form>

How do I make it so that submission is done automatically? (without
pressing the button)

I've added this but it says 'object doesn't support this property'
<script language="javascript">
<!--
if(document.all){
frm=document.all.formpurchase
}
if(document.getElementById){
frm=document.getElementById("formpurchase")
}
if (frm) frm.submit();
-->
</script>


Thanks
MA

.