First some setup valid for all timer creations...

void CPROC TimerProc( PTRSZVAL user_data )
{
    // user_data of the timer is the 'user' parameter passed to AddTimer(Exx)
}

you might want to save this for something like RescheduleTimer

_32 timer_id;
   
   

Create a simple timer, it will fire at 250 milliseconds from now, and again every 250 milliseconds from the time it starts.

timer_id = AddTimer( 250, TimerProc, 0 );

Create a timer that fires immediately, and 732 milliseconds after, passing some value 1234 as user data...

timer_id = AddTimerEx( 0, 732, TimerProc, 1234 );