Function trimestre(dates)
mois = CInt(Format(dates, "mm"))
If mois = 1 Or mois = 2 Or mois = 3 Then trimestre = 1
If mois = 4 Or mois = 5 Or mois = 6 Then trimestre = 2
If mois = 7 Or mois = 8 Or mois = 9 Then trimestre = 3
If mois = 10 Or mois = 11 Or mois = 12 Then trimestre = 4
End Function
Sub test()
Dim debut As Date
Dim trimestre As Integer
debut = InputBox("Date?")
trimestre = trimestre(debut)
MsgBox trimestre
End Sub