Instead of me going into a dissertation of how to eradicate Carpenter Bees (or any other bee for that matter), go to your favorite WEB Search Engine, search the WEB, and read what to do (directly).
I suggest you go to AltaVista as a Search Engine and enter in the folllowing EXACTLY:
+"carpenter bees" & +kill
... then press Search. You'll get quite a few 'hits' on the subject of what you need to do to eradicate Carpenter Bees. There's also info on how to tell if, in fact, you have this type of bee. (You need to make sure of your culprit first.) Anyway, print the pages out that are of use to you and go to your local Home Center. (If you don't have a printer, save the web pages to a file, and save the file to a disk, and give it to a friend who can take each page and go onto the WEB and print it out for you. NOTEPAD is a simple file editor in which to save the web pages of your choice.)
Best to ya. If you aren't having any success with the WEB search, buy a friend a few beers who knows how to search the WEB and let them teach you. This is an invaluable skill that would be very apropos for your 'question'.