>>If the interaction between modules is clean and well-defined, so that separate 'applications' can clearly be seen, you can compile each as a separate .EXE or .APP, and then have a main executable that calls them as appropriate that handles the 'single main menu' and provides the underlying support structures for the whole application.
>>
>>This is a common approach for other large applications, especailly where there are clearly separate (and preferably, marketable!) modules like accounting systems in the comemrcial environment.
>
>I did a quick test and what happened when I called another .APP was that it returned to the READ EVENTS in the calling .APP. The result was that it was no longer able to reference the forms and programs in the called .APP.
>
>How do I get the focus to stay in the called .APP?

One way that works:

Have the main .PRG in the .APP just do a RETURN. Now, all the Forms, .PRGs, etc, are available to be called.

So from your main .APP, you make 2 calls.
1) DO otherapp.APP
2) DO FORM forminotherapp

This should keep all the functions from your main .APP available, and give you access to things in the other .APP as well.