One of the weak links in the Mach VB is that all the parts of a VB application must be in the one file- either one button script, or one macro. So you cannot have a Declare File. You can, of course, declare (DIM) variables, etc at the top of any file, and you can have multiple subroutines in the file. What you cannot do is call a subroutine that is part of one button script from another button script.
Note a screen can have an init file, init.m1s in the same folder with the screen file. The init code will run before the its screen is opened. You cannot DIM objects there for use in your screen, but you can set DROs, and LEDs for initial values.
Since the Cypress docs talk about things like declare file I assume it would be possible for a better VB environment, just not the way Mach uses the scripting engine.