How do I get my slider to move when I click the groove

Question

TheI have created a simple Adobe Flash movie which is to act as a slider control. The code that I have written is shown below. I am able to grab the slider and move it to any position on the groove but I wish to also be able to click anywhere on the groove so that the slider will jump and lock to that position.
I have created a function:
groove_1.onMouseDown = function(){
      trace('You clicked x = '  + this._x);
      slider_1._x = this._x;
the problem is that the this._X coordinate returns the left-hand edge of groove_1 and not be positioned that was clicked on this control.
Can someone tell me how to get this information out of the mouse down event?
The code of the file is:
slider_1.onPress = function(){
        this.startDrag(true, _root.groove_1._x, _root.groove_1._y, _root.groove_1._x + 520, _root.groove_1._y );
slider_1.onRelease = function(){
        this.stopDrag();
slider_1.onMouseMove = function(){
        newPoint = new Object();
        newPoint.x = this._x;
        newPoint.y = this._y;
        _root.groove_1.globalToLocal(newPoint);
groove_1.onMouseDown = function(){
        trace('You clicked x = '  + this._x);
        //slider_1._x = this._x;
The source file is contained in the attached zip file

Answer 1

Hi Ned,
Thank you for your help. Your 2nd solution led me straight to the correct solution which is:
slider_1._x = this._xmouse + groove_1._x;
I use the object variable this instead of groove_1 as I am calling it from the function:
groove_1.onMouseDown = function(){
    slider_1._x = this._xmouse + groove_1._x;;
I also add the groove_1 left hand offset (groove_1._x;)
Thanks again for you help.