If the EAV program is a good one like my naturopath uses, then all he needs to do is placing the pen on the right accupuncture points and make sure there's good contact (all the navigation is very simple and straight forward to do).
He first needs to get an overall picture by getting a base of overall energy on several meridians and then prioritize as to which meridian/organ needs to be worked on first - he then chooses a range of homeopathics/supplements that he thinks it may help- the EAV will confirm whether or not it is helpful.
You should educate yourself a bit before going there so that you get tested on what you think it may be giving you problems or helping your condition like certain foods etc.
Mike