You need to use a counter to wait a bit after shooting. Heres some sample code to give the idea
Code:
var can_shoot:Boolean = true;

on Keypress... // whatever, I forgot as2
{
  if(can_shoot==true)
  {
       //shooting code
       // .....
       can_shoot = false;
       setInterval(resetShooting,20) //I forgot if this duration was seconds or miliseconds
  } 
}

function resetShooting()
{
   can_shoot = true;
}