Excel Verschachtelung

Sub VerbrauchEintragen()

 ->Zeilendefinitionen
  Const c_ERSTE_WERTEZEILE = 2
 ->Spaltendefinitionen
  Const c_SP_FZG_IG = 1
  Const c_SP_FZG_VERBRAUCH = 2
  Const c_SP_FZG_KMSTAND = 3
  Const c_SP_SPEZIFISCHERVERBRAUCH = 4
  
  Dim ws As Worksheet, l_Rows As Long
  Dim d_km_Stand_End As Double, d_km_Stand_Anf As Long
  Dim d_Verbrauch As Double
  
  Set ws = ActiveSheet
  l_Rows = ws.Cells(ws.Rows.Count, c_SP_FZG_IG).End(xlUp).Row
  
  For x = l_Rows To c_ERSTE_WERTEZEILE Step -1
   ->letztes Auftreten der FzgId vor der aktuellen Zeile suchen
    For y = x - 1 To c_ERSTE_WERTEZEILE Step -1
      If ws.Cells(x, c_SP_FZG_IG).Value = ws.Cells(y, c_SP_FZG_IG).Value Then
        d_km_Stand_End = ws.Cells(x, c_SP_FZG_KMSTAND).Value
        d_km_Stand_Anf = ws.Cells(y, c_SP_FZG_KMSTAND).Value
        d_Verbrauch = ws.Cells(x, c_SP_FZG_VERBRAUCH).Value
        If d_km_Stand_End <= d_km_Stand_Anf Then
          ws.Cells(x, c_SP_FZG_KMSTAND).Select
          MsgBox ( _
            Fehler: Kilometer-Anfang <= Kilometer-Ende & vbLf & vbLf & _
            in Zeile  & y &  km-Anfang =  & d_km_Stand_Anf & vbLf & _
            in Zeile  & y &  km-Ende   =  & d_km_Stand_End & vbLf & _
            --> Abbruch)
            Exit Sub
        End If
        If d_Verbrauch <= 0 Then
          ws.Cells(x, c_SP_FZG_VERBRAUCH).Select
          MsgBox ( _
            Fehler: Verbrauch in Zeile <= 0 & vbLf & _
            in Zeile  & x &  Verbrauch =  & d_Verbrauch & vbLf & _
            --> Abbruch)
            Exit Sub
        End If
        d_spez_Verbrauch = _
          d_Verbrauch * 100 / (d_km_Stand_End - d_km_Stand_Anf)
        ws.Cells(x, c_SP_SPEZIFISCHERVERBRAUCH).NumberFormat = 0.0 
        ws.Cells(x, c_SP_SPEZIFISCHERVERBRAUCH).Value = d_spez_Verbrauch
        Exit For
      End If
    Next y
  Next x
  Set ws = Nothing
End Sub