Bonjour,
Essaie ainsi :
Public Sub DEMO()
Dim wb As Workbook
Dim ws As Worksheet, ws2 As Worksheet
Dim tbl As Variant, v As Variant
Dim Dict As Object
Dim i As Long
Set wb = ActiveWorkbook
Set ws = wb.Worksheets("Feuil1")
Set ws2 = wb.Worksheets("Feuil2")
Set Dict = CreateObject("Scripting.Dictionary")
Application.ScreenUpdating = False
tbl = ws2.Cells(3, 1).CurrentRegion.Value
For i = 2 To UBound(tbl)
If Dict.exists(tbl(i, 1)) Then
Dict(tbl(i, 1)) = Dict(tbl(i, 1)) + tbl(i, 3)
Else
Dict.Add tbl(i, 1), tbl(i, 3)
End If
Next i
tbl = ws.Cells(1).CurrentRegion.Value
For i = 2 To UBound(tbl)
For Each v In Dict.keys
If tbl(i, 1) = v Then
tbl(i, 3) = Dict.Item(v)
Exit For
End If
Next v
Next i
ws.Cells(1).CurrentRegion.Value = tbl
Set Dict = Nothing
Set ws2 = Nothing: Set ws = Nothing
Set wb = Nothing
End Sub