Problem with a Periodic Timer firing signals

Hi,
here is what I’m trying to do:
I create a timer that should send a signal to the current thread each time,
without affecting the other threads of my process:

[…]
SIGEV_SIGNAL_THREAD_INIT(&event, SIGUSR1, 0, 0);
timer_create(CLOCK_REALTIME, &event, &timerID);

But when a call
timer_settime() to start or change the timer from another thread, the
signals aren’t send to the original thread anymore, but to the one calling
timer_settime().
My question is:
It is possible to change a timer without affecting the thead it sends the
signals to ?

Thank you,
Markus