Finalement j'ai pris cette option
Sub chifounou()
Dim rng As Range
Set rng = Range("B2:C4")
Cells(5, "B").Formula = "=COUNTBLANK(" & rng.Address & ")"
If Cells(5, "B") = rng.Cells.Count Then
MsgBox "The Range is empty"
Else
MsgBox "The Range is not empty"
End If
End Sub