Me again.
Weird, but I'm solving this one myself. For anyone who wants the answer or the script to do this, this has been tested and works:
<script type="text/javascript">
function AdJump()
{
window.location = 'http://www.a51net.com/login/'+ document.getElementById('adnum').value +'.html';
return false;
}
</script>
<form action="http://www.a51net.com/login/#.htm"
method="post" onsubmit="return AdJump()">
<p align="center"> <input id="adnum" type="text" value size="4" maxlength="4">
<br>
<input type="submit" value="Login" style="color: #FFFFFF; font-family: Verdana; font-size: 8pt; font-weight: bold; border: 1px solid #4A94DE; background-color: #4A94DE">
</p>
</form>
Well, there you go!
BG