Anyways, rereading your start Greg it sounds like a start for a joke...."The good news is that there's nothing actually wrong with the way your code is written (apart from the fact that it doesn't actually work!) "....:-D kinda funny statement...:-D...but true one...;-).

So I was rly curious if my idea gonna work and it actualy does. So here goes the code that solves my issue with the name of macros....;-)

Sub menu_cmd_1_Click()
Dim Plant As String
frm_menu_months.Hide
frm_wait.Show False
DoEvents
Application.ScreenUpdating = False
Dim i As Integer
Dim j As Integer
For i = 0 To menu_lbx_1.ListCount - 1
    If menu_lbx_1.Selected(i) = True Then
        For j = 0 To menu_lbx_2.ListCount - 1
            If menu_lbx_2.Selected(j) = True Then
                If InStr(menu_lbx_1.List(i), "C") > 0 Then
                    Plant = Replace(menu_lbx_1.List(i), "C", "D")
                    Application.Run Plant & "_" & menu_lbx_2.List(j)
                Else
                    Application.Run menu_lbx_1.List(i) & "_" & menu_lbx_2.List(j)
                End If
            End If
        Next j
    End If
Next i
Application.ScreenUpdating = True
frm_wait.Hide
End Sub
HUGE thx to Greg to address the issue

Best regards

Soul