Sub calCoeff()
Dim i As Integer
Dim DerLig As Long
With Worksheets("Moyenne_Mobile")
DerLig = .Range("A" & .Rows.Count).End(xlUp).Row
For i = 2 To DerLig - 2
.Cells(i + 1, 3).Value = Application.WorksheetFunction.Average(.Range(.Cells(i, 2), .Cells(i + 3, 2)))
.Cells(i + 2, 4).Value = Application.WorksheetFunction.Average(.Range(.Cells(i + 1, 3), .Cells(i + 2, 3)))
Next i
.Range(.Cells(DerLig - 1, 4), .Cells(DerLig, 4)).ClearContents
End With
End Sub