Thanks Adam. I remember removing that SetMouseEvents() method from the sample documentation because the method was not found. I see now I have to add this in myself.
After adding the above code, when rolling over, my custom buttons have a border around them which is not quite the effect I was hoping for. I'm using the outlook 2007 theme and when rolling over the other icons I get the dark gray background. My icons just have the black border. Do I need to make a second image file to be displayed or is there something else I'm missing?