Function datedanslemois(d As Variant) As Boolean
If IsDate(d) Then
datedanslemois = (Year(Now) = Year(d)) And (Month(Now) = Month(d))
Else
datedanslemois = False
End If
End Function
Sub test()
MsgBox datedanslemois(Now)
MsgBox datedanslemois("15/01/1960")
End Sub