No, Or you will end up with random certificate that as absolutely 0 value. If you need one to get a job and your already really good in design I would suggest you to take the cheapest course in a local school and focus on your portfolio instead of your peace of paper.
I agree with the previous comment, in design jobs is more important to have a good portfolio than a certificate. now if you want to learn online there are some e-learning sites, i know http//:jukeboxlesosns.com you can learn in real time cia skype. the price vary depending on the teacher. Good luck.