...

int check_for_event_1 = 0;
DateTime event_1_start;
double event_1_wait;

void StartEvent1(double wait_time_ms)
{
   check_for_event_1 = 1;
   event_1_start = DateTime.Now;
   event_1_wait = wait_time_ms;
}

...

// Somewhere when the event should start
StartEvent1( 1000 * 30 );

...

public void Tick()
{
...
   if( check_for_event_1 == 1 ) // If we need to check this event
   {
       TimeSpan delta = DateTime.Now - event_1_start; // calculate time between start and now
       if( delta.TotalMilliseconds > event_1_wait ) // check for expiration
       {
           check_for_event_1 = 0; // disable it if needed (only execute once)

           // TODO: Execute logic for when the event happens

           // If you need it to happen again
           //StartEvent1( 1000 * 30 );
       }
   }
...
}

...