Urgent help! mouse problem

[color=#003366]Hi,
I need urgent help!!!
this is the script:[/color]

[color=#003366]nClipEvent(load){
kretanjeX=10;
kretanjeY=10;
}[/color]

[color=#003366]onClipEvent(enterFrame){
_root.maska._x += kretanjeX;
_root.maska._y += kretanjeY;
}[/color]

[color=#003366]onClipEvent(enterFrame){
if((_root._xmouse < 155) and (_root._ymouse < 440)and
(_root._xmouse > 23)and (_root._ymouse > 30)){
_root.maska._x +=(_root._xmouse-_root.maska._x).5;
_root.maska._y +=(_root._ymouse-_root.maska._y)
.5;
}
}[/color]

[color=#003366]onClipEvent(enterFrame){
if (_root.maska._x >= 155){
kretanjeX=-kretanjeX;
}else if (_root.maska._x <= 23){
kretanjeX=-kretanjeX;
}else if (_root.maska._y >= 440){
kretanjeY=-kretanjeY;
}else if (_root.maska._y <= 30){
kretanjeY=-kretanjeY;
}
}

the problem is If I move mouse fast away circle stops moving.
how do I solve this problem?[/color]