Function DateExiste(deb&, fin&, DebutProjet As Range, FinProjet As Range)
If deb = 0 Then End 'sécurité si effacement
Dim a() As Boolean, i&, dat&
ReDim a(1 To DebutProjet.Count, 1 To 1)
For i = 1 To UBound(a)
For dat = deb To fin
If dat >= DebutProjet(i) And dat <= FinProjet(i) Then a(i, 1) = True: Exit For
Next dat, i
DateExiste = a 'vecteur vertical
End Function