Private Sub Worksheet_Change(ByVal Target As Range)
If Range("A1") = "1" Then
With Range("B1").Validation
.Delete
.Add Type:=xlValidateList, AlertStyle:=xlValidAlertStop, Operator:= _
xlBetween, Formula1:="A,B,C"
End With
Range("B1") = "1"
Else
If Range("A1") = "2" Then
With Range("B1").Validation
.Delete
.Add Type:=xlValidateList, AlertStyle:=xlValidAlertStop, Operator:= _
xlBetween, Formula1:="ONE,TWO,THREE"
End With
Range("B1") = "ONE"
End If
End If
End Sub