Function Presence%(deb#, fin#, titre As Range, plage As Range)
Dim c As Range, a As Range
For Each c In Intersect(titre, titre.Parent.UsedRange)
If c <> "" Then
Set a = Intersect(c.EntireColumn, plage)
Presence = Presence - (IIf(fin < a(1, 2), fin, a(1, 2)) - IIf(deb > a, deb, a) > 1 / 10000) 'True => -1
End If
Next
End Function