When I need to create a fully-customized form, I usually just create a webpage (in my case in ASPX) and then call CAPA via a webservice and pass the values that I need to start the job.
Not only does it load a lot faster than an IRF, I can capture the user's credentials, and don't have to give them access to CAPA itself (since it usually isn't required).
Plus you can customize it to your heart's content, and make the page blend in with your normal intranet's look if you want, so the users don't even notice the difference.
Ian