Before you do that...
I was intrigued by this question and actually was able to find a scripted solution for it. However, this would still require you to copy a standard function group in the backend (to simulate the search help call), and is somewhat cumbersome, but it works.
The only thing I'm struggling with is the case when the user enters a wrong filter value for the movement type, because then there is no valid result and I seem to have a hard time finding a way to return to the screen.
I'm not sure if this avenue is even interesting for you, so let me know. I may be able to spend some more time on this in the next few days.
Edit: Never mind, my solution still requires something that's only available in SP3. So this won't help you in SP2, I'm afraid.
Message was edited by: Tamas Hoznek