This message is sent to the currently active communication object by the communication object who wants to withdraw from the communication chain.

param1
    HWND   hwnd        /*  The handle of the object to be withdrawn from the communication chain. */

param2
    HWND   hwnd        /*  Window containing the handle of the object to be replaced. */

returns
    ULONG  ulReserved  /*  Reserved value, should be 0. */