From: lafaix@ibm.net (Martin Lafaix)

Using DosDevIOCtl functions is not sufficient if you use PM: you also
need to call WinSetKeyboardStateTable.

#define INCL_DOSFILEMGR
#define INCL_DOSDEVICES
#define INCL_DOSDEVIOCTL
#define INCL_WININPUT

#include <os2.h>
#include <stdio.h>

VOID SetNumLockState(BOOL bSet) /* if bSet is true, enable NUMLOCK */
{
  SHIFTSTATE ss;
  BYTE KeyState[257];
  BOOL bSet;
  APIRET rc;
  ULONG ulAction, ulLength;
  HFILE hf;

  rc = DosOpen("KBD$",
               &hf,
               &ulAction,
               0L,
               0,
               FILE_OPEN,
               OPEN_ACCESS_READONLY|OPEN_SHARE_DENYNONE,
               0);

  /* reading keyboard state */
  ulAction = 0;
  ulLength = sizeof(ss);
  rc = DosDevIOCtl(hf,
                   IOCTL_KEYBOARD,
                   KBD_GETSHIFTSTATE,
                   0,
                   0,
                   &ulAction,
                   &ss,
                   sizeof(ss),
                   &ulLength);

  WinSetKeyboardStateTable(HWND_DESKTOP, KeyState, FALSE);

  /* changing state -- if bSet is true, enables NUMLOCK */
  if(bSet)
    {
    KeyState[VK_NUMLOCK] |= 0x01;
    ss.fsState |= NUMLOCK_ON;
    }
  else
    {
    KeyState[VK_NUMLOCK] &= ~0x01;
    ss.fsState &= ~NUMLOCK_ON;
    }

  /* seting keyboard state */
  WinSetKeyboardStateTable(HWND_DESKTOP, KeyState, TRUE);

  ulAction = sizeof(ss);
  ulLength = 0;
  rc = DosDevIOCtl(hf,
                   IOCTL_KEYBOARD,
                   KBD_SETSHIFTSTATE,
                   &ss,
                   sizeof(ss),
                   &ulAction,
                   0,
                   0,
                   &ulLength);

  rc = DosClose(hf);
}