Sub Remplacer()
Dim ws As Worksheet
For Each ws In ThisWorkbook.Sheets
If ws.Name Like "Graph*" Then
ws.Range("M36:R45").Replace What:=ws.Range("M6").Value, Replacement:=ws.Range("M5").Value, LookAt:=xlPart _
, SearchOrder:=xlByRows, MatchCase:=False
End If
Next ws
End Sub