Yeah. In fact, there was a problem like this one a week or so ago. Something like this, if I recall...

Code:

---

var inc;
var status_accel = 0;
define speed, skill2;
function change_speed()
{  
status_accel = 0;  
wait(1); 
 my = player; 
 status_accel = 1; 
 if(my.speed <= 0) 
{ inc = 1; } 
 else { inc = -1; }  
  while(status_accel)  
{   
 my.speed += 0.1 * inc * time_step;  
      if(my.speed >= 3 || my.speed <= 0)  
   {      
 status_accel = 0; 
   }       
 wait(1);  
}
}

---

Obviously, it doesn't solve your problem. But you should be able to pick that apart to get a solution. Good practice, anyways. (btw, It shouldn't be hard to alter to get it to turn around at the top without another key press.)