The problem with classes is that they can teach you how to do things once or twice, but to really get Excel buried into the brain, repetition is the key.
I've been working with Excel since 1999; Quattro pro before that, and Lotus 123 before that. I consider myself an expert, but I'm comparing myself to the general population. If the grading curve is based on the Mr Excel site alone, I'm not sure I could qualify for Expert level.
It's going to take real world practice to get to Master level. Excel is like a Doctor's Practice; continuing education and repetition. You can be a specialist in one area of Excel or you can be a generalist and try to be good at all things.
That's why I spend time on this site trying to help others; it hones my skills and gets me exposed to issues I wouldn't normally come in contact with.
I wish you good luck
Jeff