This function indicates the mode for the generation and processing of messages for the private window class of an application.

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

HAB     hab;           /*  Anchor block handle. */
PSZ     pszClassName;  /*  Window class name. */
LONG    lControl;      /*  Message mode identifier. */
BOOL    rc;            /*  Message delay indicator. */

rc = WinSetMsgMode(hab, pszClassName, lControl);