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Function FctRE13(Plage As Range) As String
Dim Cont1 As Boolean, Cont3 As Boolean, Adja1 As Boolean, Adja3 As Boolean
Cont1 = WorksheetFunction.CountIf(Plage.Columns(2), 1) > 0
Cont3 = WorksheetFunction.CountIf(Plage.Columns(2), 3) > 0
Adja1 = WorksheetFunction.CountIf(Plage.Columns(1), 1) > 0 _
     Or WorksheetFunction.CountIf(Plage.Columns(3), 1) > 0
Adja3 = WorksheetFunction.CountIf(Plage.Columns(1), 3) > 0 _
     Or WorksheetFunction.CountIf(Plage.Columns(3), 3) > 0
If Cont1 And Cont3 Then FctRE13 = "R": Exit Function
If Cont1 And Adja3 Or Cont3 And Adja1 Then FctRE13 = "E": Exit Function
If Cont1 Then FctRE13 = "1": Exit Function
If Cont3 Then FctRE13 = "3": Exit Function
FctRE13 = ""
End Function

=FctRE13(B$1:D$5)