Sub gesamt_stream()
Dim zelle1 As String
Dim zelle2 As String
Dim actcell As Range
Dim zellnrF As Long
Dim Zellnract As Long
Dim zellnrL As Long
'Dim WS As Worksheet
'WS = ActiveSheet.Name
zellnrF = InputBox("Bitte geben Sie die erste zu summierende ZeilenNummer" & _
"ein (z.B. 8)")
zellnrL = Cells(Rows.Count, 1).End(xlUp).Row
MsgBox zellnrL
Zellnract = zellnrF
zelle1 = ("F" & zellnrF)
zelle2 = ("F" & Zellnract)
ActiveCell = ("G" & Zellnract)
ActiveCell.FormulaLocal = "=SUMME(" & zelle1 & ":" & zelle2 & ") + Summe(F2:F3)"
While Zellnract <= zellenrL
    Zellnract = Zellnract + 1
    zelle2 = ("F" & Zellnract)
    ActiveCell = ("G" & Zellnract)
    ActiveCell.FormulaLocal = "=SUMME(" & zelle1 & ":" & zelle2 & ") + Summe(" & _
      "F2:F3)"
Wend
End Sub

Gruß Armin

P.S.: always look on the bright side of Life!