How do I program the x button?

You don't do that exactly, but you can do this.

Capture the Event (Unload) on that form, and choose to close it or not, or to do something else.
Try this:

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Private Sub Form_Unload(Cancel As Integer)

    MsgBox ("This will appear when I click the x button !!! ")

    if (I_Want_To_Close_This_Window) Then
           
           'Close all files and handles

           Cancel = 0      'This means that this event will get passed on
    Else
           'Do something else

           Cancel = 1     'This means that this event will NOT get passed on
    End If

End Sub

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Greetings