This program is to create and distribute HVAC Diffusers with tow system scales, Imperial & Metric and 3 scales for the Metric system ( 1.0, 100.0 1000.0 ) with quite full options that any user may need along with new replacement dialog to replace Diffusers with full options also as in the original dialog of the program.
AUTODESK WEBSITE : THIS LINK
Tharwat Al Choufi 
How to install the program because .VLX extension.
Very simple, Just get your option from the following link:
https://autolispprograms.wordpress.com/how-to-load-an-autolisp-program/
WHAT IS THE CATCH ABBREVIATION NAME OR IF THE‘RE SUPPORTED VIDEO