To get the kind of temp you want, you have to be able to explain what you want. Temporary staffing agencies can do a lot for your company, but they can't read your mind.
If you want a QuarkXPress pro to design and put together your company newsletter, you should ask your temporary agency staffer
If you've been specific with your requests in the past and still haven't received the kind of help you want, a couple of different issues might be at the root of the problem. First, you may have called too late. Calling the day before you need a temp doesn't allow the agency much time to locate the right temp for the job. Even if the agency can track down someone with the skills you want, that person may already be booked by another company that called further in advance. Booking as far ahead as possible will increase your chances of getting a temp with the right skills. If you are looking for someone with highly specialized skills, contact multiple temp agencies to increase your chances of landing the right temp.
Second, the temp might have told the agency he had skills that he really doesn't. If you think this is the case, consider sending the temp home at noon and giving the agency a ring. Explain what you requested and that the temp showed up without those skills. Chances are, your phone call will prompt more training, or it may just prompt more honesty on the behalf of the temp in describing his skills. Either way, you're guaranteed to receive a more appropriately skilled temp the next time you call the agency.