Enter in ASP

I'm writing on a asp-project with difficult end-users
They want after filling in a textbox, to be able to press enter instead of clicking a button

Does anybody know how to intercept this?

Another thing
does anybody know how to make a combobox intelligent?
When you type a letter the list will be sorted to that letter
and when you type 2 (i.e. AK) then the list will be sorted to the
items wich start with AK

Please help

tnx for searching with me but i've found it

this is de function

function CatchEnter(myfield, e)
{
var keycode;
if (window.event) keycode = window.event.keyCode;
else if (e) keycode = e.which;
else return true;

if (keycode == 13)
{
cdmZoek3_onclick();
//myfield.form.submit();
return false;
}
else
return true;

}
and this is the line which calls it
<input type="text" class="button" name="txtparameter" onkeypress="return CatchEnter(this, event)">