This function is intended for use in a distributed application.

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

HAB     hab;    /*  Anchor-block handle. */
LONG    lMode;  /*  Synchronization mode. */
BOOL    rc;     /*  Success indicator. */

rc = WinSetSynchroMode(hab, lMode);