Kako da oduzmem...?

Evo koji problem ima...

Ovako mi izgleda formula za sabiranje

Private Sub brpacU_Change()
Dim s As String, KK As Double
If X > 0 Then
Exit Sub
End If
If Not ActiveWorkbook.Worksheets("PROTOKOL").Cells(LL, 15).HasFormula Then
ActiveWorkbook.Worksheets("PROTOKOL").Cells(LL, 15) = "=SUM(N" & LL & " :M" & LL & ")"
End If
End Sub

PITANJE

KAKO DA URADIM DA MI TE CELIJE ODUZIMA ???