VS 2010 Hey All, I am trying to "encrypt" a string but substituting all the letters with....

Hey All, I am trying to "encrypt" a string but substituting all the letters with different letters:

I.E.

String =

"A box is cool."

and a = b, b = c, c = d, .... etc so it outputs:

"B cpy jt dppm."

Any idea how I can accomplish this?
BTW I am very new to Visual Basic, I am going through an online Video Course right now and am trying to pick somethings up. I have done several things in Console (just basic stuff) and am now moving to forms....

Any help woudl be appreciated.. Also if it is not too much trouble, if you post code could you comment it and tell me what its is doing as sometimes I have trouble understanding what I am looking at if I have not seen it before. Thanks in advance!