Where are you declaring them?

If you declare them in a module, then you can use them as is anywhere.

If you declare them on a form, then to be used else where you need to preface them with the form name.

Example:
Code:
'in a module
Public Hack As String

'on a form
Hack = "Test"

'on form1
Public Hack As String

'on another form
Form1.Hack = "Test"