You can do it in excel but for that you need to have profound knowledge of statistics. Further, if your experiment has few biological replicates, you should use are more sophisticated tool that will borrow information on variance across different genes and thus achieve a greater sensitivity for detecting differentially expressed genes - check out 'limma'. If you are unfamiliar with R you probably need to find a bioinformatician to collaborate with.

Check out galaxy.org in text manipulation section. If you have bioinformatics background then R is the easiest way otherwise command line in shell terminal could also do the job using sort and unique or duplicated (depends on the table).

Best

I would recommend “R”