BCGControlBar Pro for MFC
void CBCGPButton::SetTooltip ( LPCTSTR  lpszToolTipText,
LPCTSTR  lpszToolTipDescription = NULL 

Specifies a new tooltip

Call this member function to associate a new tooltip text with the button. If the lpszToolTipText parameter is NULL the tooltip is disabled.

lpszToolTipTextPointer to the text for the tooltip
lpszToolTipDescriptionPointer to the text for the tooltip description