Function MFC(dat As Range, deb#, fin#) As String
Dim c As Range, d, f
deb = Round(deb, 6): fin = Round(fin, 6)
For Each c In dat.Parent.Range("A6:A180") 'à adapter
If c = dat And c.Row <> dat.Row Then
d = Round(c(1, 2), 6): f = Round(c(1, 3), 6)
If d <= deb And f >= fin Then MFC = "R": Exit Function
If d >= deb And d <= fin Or f >= deb And f <= fin Then MFC = "O"
End If
Next c
End Function