visual+basic+excel - Declaring variables

I've declared a byte variable as public at the start of a form.

A process in this form opens another form which gives an integer value (1 or 0) to the variable, and then the main form should take the variable value forward.

The only way I found to avoid an undefined compile error was to define the variable at the start of both forms (both as public), but the variable value isn't read across from one form to the next.

Thanks