Bonjour,
insère ce bout de code dans le module de ta feuille 1
et depuis la fenêtre VBA, sélectionne :
Outils, Références et coche Microsoft Scripting Runtime
Sub try()
Dim aa As Variant, nn As Variant
Dim myRange As Range
Dim Dico As Object
Dim a As Long, b As Long, c As Long
Application.ScreenUpdating = False
Set Dico = CreateObject("scripting.dictionary")
If Not IsEmpty(Range("B2")) Then
Set myRange = Range(Range("A2"), Range("B2").End(xlDown))
myRange.Offset(, 2).Resize(myRange.Rows.Count, 1).ClearContents
aa = myRange
For a = LBound(aa) To UBound(aa)
Dico(aa(a, 1)) = (aa(a, 2))
Next a
nn = Dico.Items
a = 2
Do Until IsEmpty(Cells(a, 2))
For b = 0 To Dico.Count - 1
If nn(b) = Cells(a, 2).Value Then c = c + 1
Next b
Cells(a, 3) = c
c = 0
a = a + 1
Loop
End If
Set Dico = Nothing
Application.ScreenUpdating = True
End Sub