1 Btn-different events

Hi
Need some help with this:

 
//Speed vars
min_speed = 1;
max_speed = 6;
beschleunigung = 1.03;
speed = 1.6;
//Clips pos
mc1._x = 0;
mc2._x = mc1.width;
mc3._x = 2*mc2.width;
mc4._x = 3*mc1.width;
 
//Changepoint
change_point = -(2*mc1._width);
//Bool vars
var drive:Boolean;
var acceleration:Boolean;
var deceleration:Boolean;
 
//_______________________________________________________________________________
//_______________________________________________________________________________
//Deceleration and stop
function anhalten() {
speed = Math.max(speed, min_speed);
this.onEnterFrame = function() {
speed>min_speed ? speed /= beschleunigung : speed=min_speed=0;
move_Clips();
};
}
//_______________________________________________________________________________
//_______________________________________________________________________________
//Default drive
function fahren() {
this.onEnterFrame = function() {
speed = 6;
move_Clips();
};
}
//_______________________________________________________________________________
//_______________________________________________________________________________
//Restart with acceleration 
function anfahren() {
speed = Math.max(speed, min_speed);
this.onEnterFrame = function() {
 
speed<max_speed ? speed *= beschleunigung : speed=max_speed;
move_Clips();
};
}
//_______________________________________________________________________________
//_______________________________________________________________________________
//Clips loop
function move_Clips() {
for (var i = 1; i<=4; i++) {
var myClips = this["mc"+i];
myClips.filters=new Array(new flash.filters.BlurFilter(2,0,2))
myClips._x -= speed;
if (myClips._x<=change_point) {
myClips._x += this._width;
}
}
}
//_______________________________________________________________________________
//_______________________________________________________________________________
//Btn events
my_btn.onRelease = function() {
if () {
trace(deceleration.valueOf());
this.gotoAndStop(2);
anhalten();
test_Txt.text = "ANHALTEN";
} else {
trace(acceleration.valueOf());
this.gotoAndStop(1);
anfahren();
test_Txt.text = "ANFAHREN";
}
};
//_______________________________________________________________________________
//_______________________________________________________________________________
fahren();//default drive

What I want to achieve is that the btn can stop the default drive by starting the function anhalten and then it should be able to restart with the function anfahren…
I think this should go with if/else and bool-vars, but I could not make it work.
Thanks for any help.