Flash CS3 Professional.
element.scaleY
Property; a float value that specifies the y scale value of symbols, drawing objects, and primitive rectangles and ovals. A value of 1 indicates 100 percent scale.
The following example sets the y scale value of the current selection to 2 (doubles its value):
var element = fl.getDocumentDOM().selection[0];
element.scaleY = 2;