How to disable the question mark of context sensitive help

I have a context sensitive help button in the caption bar of my property sheet which I want to use for about dialog box. I do not want the question mark when the button is cliked.
Instead it should pop up an About dialog box. Also I want to change the bitmap to the logo of my application. Can somebody help me out on this?
Or instead of all these, can I create a button(Icon) in the caption bar on clicking which About dialog box should pop up.
Hoping to get a solution for this problem...
TIA,
Subha