Why do I get an error when running the code for an UserForm from a standard module?

hi, this code returns an error "variable not defined" and i don't know why.

So i have this form that does all the macros in the ok button, here it is:

Private Sub OkButton_Click()

    Application.ScreenUpdating = False

    Select Case ComboBox_LocalCost.ListIndex
        Case 0
            Set UnitCostColumn = Range("A:A")
            localcosttester.Caption = UnitCostColumn.Address

        Case 1
            Set UnitCostColumn = Range("B:B")
            localcosttester.Caption = UnitCostColumn.Address

        Case 2
            Set UnitCostColumn = Range("C:C")
            localcosttester.Caption = UnitCostColumn.Address

        Case 3
            Set UnitCostColumn = Range("D:D")
            localcosttester.Caption = UnitCostColumn.Address

        Case 4
            Set UnitCostColumn = Range("E:E")
            localcosttester.Caption = UnitCostColumn.Address

        Case 5
            Set UnitCostColumn = Range("F:F")
            localcosttester.Caption = UnitCostColumn.Address

        Case 6
            Set UnitCostColumn = Range("G:G")
            localcosttester.Caption = UnitCostColumn.Address
        Case 7
            Set UnitCostColumn = Range("H:H")
            localcosttester.Caption = UnitCostColumn.Address

        Case 8
            Set UnitCostColumn = Range("I:I")
            localcosttester.Caption = UnitCostColumn.Address

        Case 9
            Set UnitCostColumn = Range("J:J")
            localcosttester.Caption = UnitCostColumn.Address

        Case 10
            Set UnitCostColumn = Range("K:K")
            localcosttester.Caption = UnitCostColumn.Address

        Case 11
            Set UnitCostColumn = Range("L:L")
            localcosttester.Caption = UnitCostColumn.Address

        Case 12
            Set UnitCostColumn = Range("M:M")
            localcosttester.Caption = UnitCostColumn.Address

        Case 13
            Set UnitCostColumn = Range("N:N")
            localcosttester.Caption = UnitCostColumn.Address
        Case 14
            Set UnitCostColumn = Range("O:O")
            localcosttester.Caption = UnitCostColumn.Address

        Case 15
            Set UnitCostColumn = Range("P:P")
            localcosttester.Caption = UnitCostColumn.Address

        Case 16
            Set UnitCostColumn = Range("Q:Q")
            localcosttester.Caption = UnitCostColumn.Address

        Case 17
            Set UnitCostColumn = Range("R:R")
            localcosttester.Caption = UnitCostColumn.Address

        Case 18
            Set UnitCostColumn = Range("S:S")
            localcosttester.Caption = UnitCostColumn.Address

        Case 19
            Set UnitCostColumn = Range("T:T")
            localcosttester.Caption = UnitCostColumn.Address

        Case 20
            Set UnitCostColumn = Range("U:U")
            localcosttester.Caption = UnitCostColumn.Address
        Case 21
            Set UnitCostColumn = Range("V:V")
            localcosttester.Caption = UnitCostColumn.Address

        Case 22
            Set UnitCostColumn = Range("W:W")
            localcosttester.Caption = UnitCostColumn.Address

        Case 23
            Set UnitCostColumn = Range("X:X")
            localcosttester.Caption = UnitCostColumn.Address

        Case 24
            Set UnitCostColumn = Range("Y:Y")
            localcosttester.Caption = UnitCostColumn.Address

        Case 25
            Set UnitCostColumn = Range("Z:Z")
            localcosttester.Caption = UnitCostColumn.Address

        Case 26
            Set UnitCostColumn = Range("AA:AA")
            localcosttester.Caption = UnitCostColumn.Address

        Case 27
            Set UnitCostColumn = Range("AB:AB")
            localcosttester.Caption = UnitCostColumn.Address
        Case 28
            Set UnitCostColumn = Range("AC:AC")
            localcosttester.Caption = UnitCostColumn.Address

        Case 29
            Set UnitCostColumn = Range("AD:AD")
            localcosttester.Caption = UnitCostColumn.Address

        Case 30
            Set UnitCostColumn = Range("AE:AE")
            localcosttester.Caption = UnitCostColumn.Address

        Case 31
            Set UnitCostColumn = Range("AF:AF")
            localcosttester.Caption = UnitCostColumn.Address

        Case 32
            Set UnitCostColumn = Range("AG:AG")
            localcosttester.Caption = UnitCostColumn.Address

        Case 33
            Set UnitCostColumn = Range("AH:AH")
            localcosttester.Caption = UnitCostColumn.Address

        Case 34
            Set UnitCostColumn = Range("AI:AI")
            localcosttester.Caption = UnitCostColumn.Address
        Case 35
            Set UnitCostColumn = Range("AJ:AJ")
            localcosttester.Caption = UnitCostColumn.Address

        Case 36
            Set UnitCostColumn = Range("AK:AK")
            localcosttester.Caption = UnitCostColumn.Address

        Case 37
            Set UnitCostColumn = Range("AL:AL")
            localcosttester.Caption = UnitCostColumn.Address

        Case 38
            Set UnitCostColumn = Range("AM:AM")
            localcosttester.Caption = UnitCostColumn.Address

        Case 39
            Set UnitCostColumn = Range("AN:AN")
            localcosttester.Caption = UnitCostColumn.Address

        Case 40
            Set UnitCostColumn = Range("AO:AO")
            localcosttester.Caption = UnitCostColumn.Address

        Case 41
            Set UnitCostColumn = Range("AP:AP")
            localcosttester.Caption = UnitCostColumn.Address
        Case 42
            Set UnitCostColumn = Range("AQ:AQ")
            localcosttester.Caption = UnitCostColumn.Address

        Case 43
            Set UnitCostColumn = Range("AR:AR")
            localcosttester.Caption = UnitCostColumn.Address


    End Select

'more code of the same procudres here...

The code becomes too big and based on my research i should assign this code on a module and just put the Run "Macro_Name" in the OK button,
but when i do it the combo boxes i have becomes unidentified variables, why is that so?