Sub Test()
Dim Cel As Range, Fml As String
Set Cel = ActiveSheet.[D1]
Do: Set Cel = Cel.Resize(Rows.Count - Cel.Row).Find("Rendement machine")
If Cel Is Nothing Then Exit Do
Fml = "=AVERAGE(R" & Cel.Row + 1 & "C:R[-1]C)"
Set Cel = Cel.End(xlDown).Offset(1)
Cel.FormulaR1C1 = Fml: Loop
End Sub