Many times a user/CAD admin will create a customer part that is to be used by several user in the organization. The ability to add help like we do with the ADS built in parts would be very convenient. There is actually a way to do this and it is documented in the online help that ships with ADS (in the customization manual) or go to the link below. Expand (press the plus sign) Customization Examples. The last topic explains how to associate an HTML file with your user part.
http://eesof.tm.agilent.com/docs/adsdoc2002C/custom/index.html
http://eesof.tm.agilent.com/docs/adsdoc2002C/custom/index.html