Const SuchZeile = "    MsgBox ""VBA macht Spa� !"""
Const NeueZeile = "    MsgBox ""VBA macht gro�en Spa� !"""

Sub VBAZeile�ndern()
    Set VBE = Application.VBE.ActiveCodePane.CodeModule
    With VBE
        For x = 1 To .CountOfLines
            If .Lines(x, 1) = NeueZeile Then
                .ReplaceLine x, SuchZeile
                Exit Sub
            End If
            If .Lines(x, 1) = SuchZeile Then
                .ReplaceLine x, NeueZeile
                Exit Sub
            End If
        Next x
    End With
End Sub

Sub Testen()
    MsgBox "VBA macht Spa� !"
End Sub