Modify javascript application

Wanting this diagram application modifying so that the angles are shown between lines. From here - [login to view URL] - click 'file' - 'new sketch' Draw two intersecting lines. Select the two lines that you have drawn (cntrl click or drag area). From here I want the user to be able to click the 'construct' tab and a new menu item of 'angles' be present. If the angles item is clicked then the script should add all the angles to the diagram between the two lines selected. Angles to be drawn with a curved line and labelled in degrees, unless a right angle in which case drawn as a square box. Thanks, Richard