Sub test()
Dim a, b, Lig, i&
a = Range("B2:B" & Range("B" & Rows.Count).End(xlUp).Row)
b = Range("C2:C" & Range("B" & Rows.Count).End(xlUp).Row)
For i = LBound(a) To UBound(a)
Lig = Application.Match(a(i, 1), b, 0)
If Not IsError(Lig) And a(i, 1) <> "" Then Cells(i + 1, 4) = Lig + 1
Next i
End Sub