how can i determine the possible expressed genes from my study..i have processed few cel files and used normalization processes such as RMA also mas5 .

I would like to know how can i determine the genes from prob level data?

thanks

You don't say enough about what you have done for anybody to give you more than generalized advice. So here is some generalized advice:

http://bioconductor.org/help/workflows/annotation/annotation/