Force url after login

I work on a script and I need to force a redirection to the %original_targeturl% after my [LOGIN_STEP1]
I need to do that because sometimes the page after LOGIN is not the page where I want to post my link.

Sven can you help me ?

This is my script plan:
[SETUP]
[REGISTER_STEP1]
[LOGIN_STEP1]
[STEP1]
[STEP2]