procedure SetCapsLockKey( vcode: Integer; down: Boolean );
begin
if Odd(GetAsyncKeyState( vcode )) < >  down then
begin
keybd_event( vcode, MapVirtualkey( vcode, 0 ),
KEYEVENTF_EXTENDEDKEY, 0);
keybd_event( vcode, MapVirtualkey( vcode, 0 ),
KEYEVENTF_EXTENDEDKEY or KEYEVENTF_KEYUP, 0);
end;
end;

...

SetLockKey( VK_CAPITAL, True ); //按下


'keybd_event', 'MapVirtualkey'和'GetAsyncKeyState'是win-api函数...