Private Sub Worksheet_Change(ByVal Target As Range)
Dim DerLig As String
DerLig = Range("A" & Rows.Count).End(xlUp).Row
If Not Intersect(Target, Range("B2:B" & DerLig)) Is Nothing Then
Application.EnableEvents = False
If Target.Count = 1 Then Target.Offset(0, 0).Value = Val(Target.Offset(-1, 0).Value) - Val(Target.Value)
Application.EnableEvents = True
End If
End Sub