programming autopilot

Hi all, as a part of my ATR cockpit I am currently in development of HT1000 GNSS - Global navigation satellite system - GPS to control lateral navigation of the plane. http://atrproject.wordpress.com/ I am just in stage, when my GNSS could feed AP by calculated required track. What I am looking for, is FSX compatible autopilot I can feed with that calculated track and which will convert-correct track into heading. I would like to know, if there is something like that already done. I've been looking for such a thing for a some time, but without success. - I can probably write my own PID formula based AP to provide heading control, but I prefer already working solution. :-)- Original idea just to correct track by wind shift to get heading is not suitable in cases, where aircraft have side shift due to internal force - rudder or asymmetric thrust for example.- If there is no out-of-the-box AP capable of this, I would welcome any hint, source code, theory background etc. to help me with writing my own one. I would welcome any idea regarding this topic. :-) RegardsLitin