If you need to save your drawing from your application, you can can check if it was changed or not with the help of GetDrawingChanged instruction.

<?xml version="1.0" encoding="UTF-8"?>
<cadsofttools version="2">
  <!-- Description: GETDRAWINGCHANGED instruction checks if any changes were made in a Drawing. Result parameter CHANGED returns True if any changed were implemeted in a Drawing. -->  
  <getdrawingchanged/>
</cadsofttools>