I received a Certificate in Marketing from UC Berkeley back in 1998. I had an Undergraduate Degree in Commumincations from another PAC 10 University back in the 80's and was in a union job at a major airline and wanted to facilitate a move into Management.
I was contemplating an MBA ,but wasn't sure at the time. This was the catalyst I needed and helped me secure my Management position.
The Extension/Certificate Programs at Berkeley are top notch. It was no slouch of a Program either. If I remember correctly I took 8 courses. I would complete a semester course in little over a month! In a six week time frame I would read entire Marketing textbook, have midterm and a final and complete a group project/presentation! Not every class was a project but about half. It took me about a year and half to complete the program.
The instructors were all either Berkeley professors or very successful in their field in the Bay Area.
So basically other than my day job, all I did was focus on the one class for an entire month including weekends.
The classes were not transferable to a Berkeley MBA program,however at the time they were acceptable to many lesser name institutions towards other degrees. I received a 3.5 GPA and really enjoyed the program immensely.
I don't have the MBA by my name, however the Program served its purpose to meet my goal.
UC System has some excellent Certificate Programs. I suggest whatever school you choose, make sure the Program meets your criteria to reach the Goal you have established for yourself.
Good Luck!