WinReplyMsg replies to a message sent from any window on a specified thread to any window on another specified thread, but that has not yet been processed by the receiving window.

#define INCL_WINMESSAGEMGR /* Or use INCL_WIN, INCL_PM, */
#include <os2.h>

HAB        hab;          /*  Anchor-block handle. */
HMQ        hmqSender;    /*  Message-queue handle of the sender. */
HMQ        hmqReceiver;  /*  Message-queue handle of the receiver. */
MRESULT    Reply;        /*  Reply passed to the sending window as the return parameter of WinSendMsg. */
BOOL       Success;      /*  Success indicator. */

Success = WinReplyMsg(hab, hmqSender, hmqReceiver,
            Reply);