BCGControlBar Pro for MFC
UINT BCGM_PROPERTY_GROUP_CHANGING

The message is sent to the owner of property list control (CBCGPPropList) when the value of property group is changing.

Parameters
wParamcontains the control ID of the property list.
lParama pointer to the property group (CBCGPProp) that is changing.
Returns
the return value is ignored.