Is it possible to reference global/public vars in cell forumulas?

I want to create a function that sets a global variable say true and false,
and have a cell formula that has an if statement:

=if([Globalvar], do something, "")

I can't use a UDF because it causes other Macros I have to fail with
RunTimeError 1004. It's something about UDFs not allowed to alter other
cells, but the UDF wouldn't be modiying cells, but my non-UDF macros are.

So, I'm experimenting with a different approach.

Ideas?