Private Sub Worksheet_Change(ByVal Target As Range)
Dim der&, i&, n&, k&
On Error GoTo FIN
Application.EnableEvents = False
der = Me.UsedRange.Row + Me.UsedRange.Rows.Count - 1
For i = 2 To der
If Not Intersect(Target, Range("b" & i & ":L" & i)) Is Nothing Then
If (Cells(i, "b") Like "M#") Or (Cells(i, "b") Like "M##") Then
n = CInt(Mid(Cells(i, "b"), 2)) - 1: n = n \ 2
If n <= 4 Then Cells(i, "c").Offset(, 2 * n).Resize(, 2).ClearContents
End If
End If
Next i
FIN:
Application.EnableEvents = True
End Sub