This function obtains the Window List handle belonging to a window.

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

HWND       hwnd;           /*  Window handle of an application. */
PID        idProcess;      /*  Process identity of the application. */
HSWITCH    hswitchSwitch;  /*  Switch list handle for the specified application. */

hswitchSwitch = WinQuerySwitchHandle(hwnd,
                  idProcess);