Hey,
Part time M.tech courses are offered in many top institutes and universities as a part of continuing education program. Classes are usually in evening and weekends therefore one must be in the close premises of the institute. These courses are offered by many IIT's, NIT's and other top universities. Eligibility involves that you must have a couple of years of regular job experience, a letter from your current employer stating that they are sponsoring you or have no objection on your studying while working in their company.

Here is a list of IIT's offering part time M.Tech courses:

http://engistan.com/mtech/list-of-iits-offering-part-time-m-tech-courses/

All the best!