CallHookHook is called for debugging purposes, whenever any other hook procedure is about to be called.

#define INCL_xxx
#include <os2.h>

HMQ      hmqCurrent;   /*  Message-queue handle associated with the current thread. */
HMQ      hmqCreated;   /*  Message-queue handle created by the installing thread. */
PID      pid;          /*  Process identity of the installing thread. */
TID      tid;          /*  Thread identity of the installing thread. */
SHORT    sHookType;    /*  Hook type. */
PFN      pfnHookProc;  /*  Address of the hook procedure that is about to be called. */
BOOL     f;            /*  Success indicator. Indicates whether or not the hook pfnHookProc should be called: */

f = CallHookHook(hmqCurrent, hmqCreated, pid,
      tid, sHookType, pfnHookProc);