Best Practice for Global Variables

I'm writing my first VB.NET application. It's a very simple application that only has 1 form.

A variable that I am declaring needs to be used in multiple procedures (2 button events to be exact). Therefore, I know that I need to declare the variable outside of the button procedure so that it is accessible by both procedures. The question is what's the best way:

Option A) Declare the variable within the form class:

Class Form

Dim MyVar

Procedure A

Do Something

End Procedure A

Procedure B

Do Something

End Procedure B
End Class Form

Option B) Declare the variable within a module that is within the same source file as the form class:

Class Form

Procedure A

Do Something

End Procedure A

Procedure B

Do Something

End Procedure B
End Class Form

Module 'This module in the same source file as the Form

Dim MyVar

End Module

Option C) Declare the variable within a seperate module

Class Form

Procedure A

Do Something

End Procedure A

Procedure B

Do Something

End Procedure B
End Class Form

Module 'This module in a seperate source file (module1.vb)

Dim MyVar

End Module

[1391 byte] By [Ryan_Small] at [2008-1-4]