I agree with Mr. Sample and Enrico. Based on previous posts by this jaggz character I have serious doubts about his competence, so I did not insert actual manual links, just manual titles, and otherwise kept it very vague. jaggz can find the manuals himself; this is something anyone who wants to become competent in this trade had better learn to do on their own rather than beg for help in places like this. Finding references on how to do something is very difficult for a beginner, and sometimes for very experienced people. I recall sometime in the last 10 years putting out on one of the news groups a wish for something I sort of wanted to do, though not something I had to do, and a wise person told me where to look for documentation about something I did not even know was possible. I added the capability to one program and it worked!
On the other hand, jaggz has tried to be helpful in other posts, so I did not want to be completely negative.
Deducing an unused user SVC in the SVC table is not difficult, but it is something jaggz should figure out himself. I won't tell him how to do it, especially since it has been many years since I looked at the SVC table, so I'd have to reinvent what I did then. I know I did it, but I don't remember exactly how I did it.