ATL OwnerDrawn ListView

I have implemented an ownerdrawn listview control using ATL 3.0. I am superclassing the standard windows listview control. However when I try to catch the WM_DRAWITEM in the main control class, I find that the event handler isn't being called.
I have set the style OWNERDRAWFIXED, so why is this happening?
Any ideas?

Thanks,
Charles Gamble,
Ireland.