danno,
kristoff gave some good advice...
its worth practicing going into trance before attempting the calculator thing. you need a deep level of trance to be able to experience hallucinations such as that, and that requires practice.
each time you go into trance, you are training your mind to go deeper. so the more practice you get, the deeper you will be able to go, and the quicker you will be able to get there.
one book i would recommend is "trance-formations" by richard bandler and john grinder (creators of nlp). it talks about self hypnosis, hypnotic phenomena (hallucinations, time distortion, amnesia, anaesthesia etc) and all sorts of stuff that you would find helpful.
the book is now out of print, so if you go to www.bookfinder.com , you can search for it there and buy it from one of the 2nd hand bookstores for a good price.
however, even if you get the book, i still recommend seeing a profesional hypnotist if you can afford it. if you are set on doing things like the calculator thing, you would save yourself an awful lot of time.
i'm not saying you cant develop the skill level by yourself to do it. i know that you can. and i know that someone like yourself will be determined enough to get there.
i'm just saying that if you can afford it, it'll be worth it.
if that isnt an option, find yourself a partner to practice with, as that will be the next best thing. having someone guide you through hypnosis is much easier than doing it by yourself. and you will also find that you are able to accomplish more. if you decide to do that, i can recommend some books to help you out.
let us know what you decide to do 
