Hi,
I had a similar project to work on Win32 application build on powerbuilder in 1999. I had a combination of spying in Win32 and Region mode. The hardest part was to spy the cells and table. For some reason App modellar was not able to spy the tables and hence i have use surface automation. If you do use region mode, make sure the color is reduced when recognizing elements and also be aware of the color of a button when it is clicked.
Hope it works out for you.
Praveen.