First, we need to set the initial size of the control to its static size using the COleControl::SetInitialSize method. This should be done in your control's constructor like this:
override OnSetExtent and return FALSE, which tells the container that the control cannot be re-sized
BOOL CFAQCtrl::OnSetExtent( LPSIZEL lpSizeL )
{
return FALSE;
}
for more refer to
http://www.widgetware.com/FAQArticle.htm#Size