Private Sub Worksheet_Change(ByVal Target As Range)
Static bDo As Boolean
Dim rng As Range
If Not bDo Then
bDo = True
Set rng = Target.Worksheet.Range("A1:A4")
If Not Intersect(rng, Target) Is Nothing Then
Dim rngValA As Range
Dim rngValB As Range
Dim rngValC As Range
Dim rngValD As Range
Set rngValA = rng.Cells(1, 1)
Set rngValB = rng.Cells(2, 1)
Set rngValC = rng.Cells(3, 1)
Set rngValD = rng.Cells(4, 1)
If Intersect(Target, rngValD) Is Nothing And rngValA = "a" And rngValB = "x" And rngValC = "n" Then
rngValD = "2"
End If
End If
bDo = False
End If
End Sub