On key press event request.form getting null

Hi friends ,
 
I have a login page in classic asp which contains two buttons login and signup . Also i have a submit button which is hidden .On form submit i am checking the
if request.form(submit) = login
 
then login steps
 
else request.form(signup) = signup
 
it works fine in all browsers but in IE when i hit the enter key it esacpe the request.form(submit) = login and request.form(signup) = signup but when i click on enter button then it works fine . Any idea why i am getting nothing on the request.form(submit) = login .