Global Functions???????

Is there a way to make global functions that can be called and used for several other jass functions.

Yes, put it in the custom text section, accessible via the map name at the head of the trigger list.

Actually, there isn't anything like private functions in JASS , the only condition to call a function is that the function you are calling it from was compiled after the function you are calling, this depends mostly on the editor, but thanks to Cubasis we know the exact way of forcing the editor to compile certain triggers first, This is because the Custom Script Section AIAndy pointed, tends to get too big and unorganized, so you can simulate modules with the making of triggers where you only put the functions.

To force a trigger to be compiled before another one, drag the trigger so it goes before the other triggers in the lists, then instantly save the editor.