For a leap year function, this should work
Code:
Private Sub Form_Load()
    MsgBox "2008 = " & IsLeapYear(2008)
    MsgBox "2009 = " & IsLeapYear(2009)
End Sub

Private Function IsLeapYear(ByVal iYear As Integer) As Boolean
Dim strDate As String

    strDate = "February 29, " & iYear
    IsLeapYear = IsDate(strDate)
End Function