Option Explicit
Sub commentaire()
Dim Cell As Range
Dim dl&
With ActiveSheet
dl = .Cells(.Rows.Count, "A").End(xlUp).Row
For Each Cell In Range("F2:F" & dl)
If IsDate(Cell.Offset(, 2)) Then
Cell.Value = "Demande traitée"
ElseIf IsDate(Cell.Offset(, 1)) Then
Cell.Value = "Demande en cours"
Else
Cell.Value = "Erreur impossible"
End If
Next Cell
End With
End Sub