MACROMEDIA FLEX-FLEX ACTIONSCRIPT LANGUAGE Reference page 191

Example
In the following script, the
conditional script is executed when the mouse is released and the object is dropped:
on (press) {
startDrag(this);
}
on (release) {
trace("X:"+this._x);
trace("Y:"+this._y);
stopDrag();
}
See also
onClipEvent()
function executes when the mouse is pressed, and the
startDrag()
on() 191