So you basically want to have F19 move left& F20 move right on the
display& F21 to split screen? Left& right are easy enough, load 2
subfiles on F20 show SFL2, F19 show SFL1, as far as the split screen you'd
have to do some fun coding. But the left/right thing is easy...it really
depends on HOW you write the program(s), etc.