Dropdown List value triggers macro.

I have a dropdown list at c19 with 4 options. I'm attempting to trigger a msgbox to prompt the user for a secondary piece of data if option 2 is selected.

the following code snippit is what I'm attempting to modify to meet my needs but it doesn't seem to be working:

Private Sub Worksheet_Change(ByVal Target As Range)

  Dim Addx As String
  Dim Rng As Range
    
    Addx = Target.Validation.Formula1
    Set Rng = Range(Right(Addx, Len(Addx) - 1))
    
    If Target.Address = "$C$19" Then
      Select Case Target.Value
      
        Case Is = Rng.Cells(1, 1)   'First Drop Down Item
          Call MacroA
        Case Is = Rng.Cells(2, 1)   'Second Drop Down Item
          Call Get_WO_NUM
        Case Is = Rng.Cells(3, 1)   'Third Drop Down Item
          Call MacroC
        Case Is = Rng.Cells(4, 1)   'Fourth Drop Down Item
          Call MacroD
          
      End Select
    End If
    
End Sub

Any assistance would be appreciated. When I pick an item from the list I get a compile error sub or function not defined.

I'm Sorry .. I did create the macros however they don't have any code in them as yet ... so the following code is in module1

Sub Get_WO_NUM()

    Range("C47").Value = InputBox( "Please Provide the Work Order #")
        
End Sub
Sub MacroA()

End Sub
Sub MacroC()

End Sub
Sub MacroD()

End Sub

the goal is simply to prompt the user for a value and place it in C47 if they select option 2 from the list.

Change the code as shown in red:-

Private Sub Worksheet_Change(ByVal Target As Range)

  Dim Addx As String
  Dim Rng As Range
    
    
   If Target.Address = "$C$19" Then
      'The two lines below are moved below the line above, Or you code will run agin when the Input Box value is inserted.
     Addx = Target.Validation.Formula1
        Set Rng = Range(Right(Addx, Len(Addx) - 1))      
      Select Case Target.Value
        Case Is = Rng.Cells(1, 1)   'First Drop Down Item
          Call MacroA
        Case Is = Rng.Cells(2, 1)   'Second Drop Down Item
          Call Get_WO_NUM
        Case Is = Rng.Cells(3, 1)   'Third Drop Down Item
          Call MacroC
        Case Is = Rng.Cells(4, 1)   'Fourth Drop Down Item
          Call MacroD
          
      End Select
    End If
  End Sub

Sub Get_WO_NUM()
Range("C47").Value = Application.InputBox("Please Provide the Work Order #")
End Sub

It works for me.
As it says "Sub Or function not Defined" it would point to one of those Subs (Call ---) not existing , Are they ????

That's going to do it. It works fine now and I very much appreciate the assistance MickG. I had to make a small adjustment to the data validation for the dropdown but it works perfectly ... thanks again and have a great day.

Your welcome
Regrds Mick