Well you could do something like:

Code:
action enemyki()
{
 var ki_active = 0;
 var seconds = total_secs;
  while(1)
  {
    if(ki_active)
    {
     //KI-code
    }
    if(seconds == total_secs - 3) // if 3 Seconds are over
     {
       seconds = total_secs;
       if(vec_dist(my.x,player.x)<900)
       {
         ki_active = 1;
       }
       else
       {
         ki_active = 0;
       }
     }
    wait(1);
  }
}