>I'm still confused. If I set the _include variable to foxpro.h then everything I do in VFP will have access to it?

No. It'll be only used by Form and Class Designers when new form/class is created to populate Include for it. It doesn't have any effect on already created forms/classes.

> Then if I create a form class (myformclass) I can set file1.h from the menu, then if I create a form (myform) from the form class I can set file2.h from the menu. Myformclass will have access to foxpro.h and file1.h? Myform will have access to foxpro.h, file1.h and file2.h?

No. Each class will have access only to the .H file you specified from the menu for it.
If you want a form/class to use multiple .H files you can create a wrapper .H file that in turn #INCLUDEs other .H files and use it for the form/class.