Dim x As Integer
Dim y As Integer
Dim z As Integer
Dim wks As Excel.Worksheet
Dim strFormula As String
Set wks = ThisWorkbook.Worksheets("Tabelle1")
x = 1
y = 1
z = 6
Do
With wks
strFormula = "=IF(ISERROR(AVERAGE(" & .Range(.Cells(y, 1), .Cells(z, 1)).Address & "))," & _
""""",AVERAGE(" & .Range(.Cells(y, 1), .Cells(z, 1)).Address & "))"
.Cells(x, 4).Formula = strFormula
End With
x = x + 1
y = y + 6
z = z + 6
Loop While x < 48 And y < 283 And z < 288