Private and Public Definitions
By default, all subroutines, functions, and user-defined types (including enumeration definitions) may be accessed from other modules. To prevent other modules from accessing procedures or user-defined types precede the definition with the Private keyword:
Private Sub MyBeep
Beep : Beep
End Sub
In contrast to procedures, the global variables defined at the top of one module are not available to other modules unless they are declared using a Public statement. When used for variable declarations, the Public statement has the same syntax as the Dim statement:
Public universal_data As String
The names of all definitions, even private ones, are visible in other modules. To avoid errors due to name conflicts you must avoid using the same procedure, type, and variable names in more than one module. A common technique for avoiding name conflicts is to append a prefix to the names of global variables and procedures. For example, if you write a module of text-processing functions, you might prefix each function name with txt, e.g., txtFunction1.