It took a lot of fiddling with the _getk routines (note to self: need more _getk documentation for the community), but I got Document DE to create new files that associate automatically with Document DE 5. Using Doors CS v4.8.5 and up, just click a Document DE 5 file and it automatically opens itself in Document DE. I also created some proprietary cursor routines to change the cursor icon depending on the location onscreen. This seems pretty much done, although there is some smudging when the cursor hits an edge. Document DE 5 continues!