VBA commands for multiple cells?

Hello, I'm a complete amateur in VBA so my question may be stupid but I really don't know how to resolve my problem. So, I have an excel table with multiple drop-down lists. However for certain cells, I'd like to have multiple options choice so I've modified to following code to work for me. The problem is that it works only for one cell and I want it to work for multiple cells but not all: For example; I want to have this multiple choice drop down lists in cells D8, D13, D18 and D21. Can you help me with that please )

Here's the code I'm using.

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Hi JLoKyM..

Please use code tag for Codes.. otherwise it really hard to read.. and you may also get an idea that.. "No One knows the answer.."

BTW.. try this..

Private Sub Worksheet_Change(ByVal Target As Range)
Dim rngDV As Range
If Target.Count > 1 Then GoTo exitHandler
On Error Resume Next
Set rngDV = Cells.SpecialCells(xlCellTypeAllValidation)
On Error GoTo exitHandler
If rngDV Is Nothing Then GoTo exitHandler
    If Intersect(Target, rngDV) Is Nothing Then
        'do nothing
    Else
        Application.EnableEvents = False
        Select Case Target.Address
            Case "$D$8", "$D$13", "$D$18", "$D$21"
                If Target.Value = "" Then GoTo exitHandler
                    If Target.Offset(1, 0).Value = "" Then
                        Target.Offset(1, 0).Value = Target.Value
                    Else
                        Target.Offset(1, 0).Value = _
                        Target.Offset(1, 0).Value _
                        & ", " & Target.Value
                    End If
        End Select
    End If
exitHandler:
    Application.EnableEvents = True
End Sub

I din't found any error in my code.. and working fine.. for me..
All IF blocked are closed..

Right click Sheet name, where dropdown Data Validation exists.. then..
paste code in the same module..
Dont use the code in New Module..

I know you are pasting the code in Sheet module only, as Worksheet_Change event triggered and highlighted with Yellow.. still for precaution..

Thanks for the feedback..

Please mark the post as solved..