The EM_SETOLEINTERFACE message gives a rich edit control an IRichEditOleCallback object that the control uses to get OLE-related resources and information from the client.
EM_SETOLEINTERFACE
wParam = 0;
lParam = (LPARAM) (IRichEditOleCallback FAR *) lpObj;
Parameters
lpObj
Pointer to an IRichEditOleCallback object. The control calls the AddRef function for the object before returning.
Return Values
Returns a nonzero value if successful or zero otherwise.