Bug in FullCalendar MouseWheel?

Hi – I’m trying to use the MouseWheel event in Full Calendar.  The below code does not work as expected.  The event actually does fire sometimes – but e.Delta is always 0 – never greater than or less than 0.  I am attaching to the event.
Private Sub SetupEvents() Handles Me.Load
AddHandler caseCalendar.MouseWheel, AddressOf CheckMouseWheel
End Sub

Private Sub CheckMouseWheel(sender As Object, e As MouseEventArgs)
If e.Delta > 0 Then MoveItemUp()
If e.Delta < 0 Then MoveItemDown()
AlertBox.Show(“Mouse wheel delta = ” & e.Delta.ToString)
End Sub