I have a question, can I take courses when I am on OPT???

I would like to work after I graduate and using my OPT. At the same time, can I take some courses on a part-time basis towards my PhD degree??

Can anybody tell if it's feasible?

Why the international student officer in our school said that I can not do that. He said I can take courses like scuba diving, but not courses towards any degree. Is this true? Anybody has any experience on it??

//bow