AS3 Dragging with inertia for dummies

Could someone give me a bit of direction? I'm sure I can find an inertia physics formula, but I don't know how to capture the mouse speed during the Mouse Down with Mouse Move, in order to use it with Mouse Up, and how to make it so that, when Mouse Up, the thing comes to a stop but the doesn't move again until I press the mouse again.

For example, this script has many problems, such as the fact the the MC keeps following the mouse even in the mouse isn't pressed.

myMC.addEventListener(MouseEvent.MOUSE_DOWN, whenMouseDown);

myMC.addEventListener(MouseEvent.MOUSE_UP, whenMouseUp);

function whenMouseDown(evt:MouseEvent):void {

     myMC.addEventListener(MouseEvent.MOUSE_MOVE, whenMouseMove);

     function whenMouseMove(evt:MouseEvent):void {

          myMC.x = mouseX; // placeholder dragging action

          // capture mouse speed?

     }

}

function whenMouseUp(evt:MouseEvent):void {

myMC.removeEventListener(MouseEvent.MOUSE_DOWN, whenMouseDown);

// add inertia here?

}

Also, how can I make the MC be dragged along with the without its X snapping to mouseX? Other stuff I tried here didn't work either?