Flash CS3 Professional.
element.x
Property; a float value that specifies the x value of the selected element’s registration point.
The following example sets the value of the specified element’s registration point to 100, 200:
fl.getDocumentDOM().getTimeline().layers[0].frames[0].elements[0].x= 100;
fl.getDocumentDOM().getTimeline().layers[0].frames[0].elements[0].y= 200;