Take a look at
this article[
^], probably it will give you some advice on how to do that...
Hope this helps.
In the DrawItem() function you may find the below code
pDC->DrawFrameControl(&rect, DFC_BUTTON, DFCS_BUTTONRADIO | (sel?DFCS_CHECKED:0));
just change this to
pDC->DrawFrameControl(&rect, DFC_BUTTON, DFCS_BUTTONPUSH | (sel?DFCS_CHECKED:0));