I need to give credits to user how offen he can post in a Board (for All Forums with the same members tabel) I try to say what i want I give 12 credits to user "Bla" now he can post 12 times when he delete one of the postings he get an credit back
I would just create another field in the members table... M_CREDITS I think all you'll need to do is update post_info.asp to add and subtract from this field when the user creates a new topic or deletes a topic (or replies?). Post_info.asp is very well formattted to easily find where the edits need to be. It should just be a few lines you'll need to update.
Then just create your pages to give the user his credits to start with.