Step one, start the program (of cource)
Step two, type in text to convert to Base64 and hit 'Text to Base64'...
Step three, type in the Base64 lines to convert back to readable text and hit 'Base64 to Text'...
Step four, check out my source code for it at: http://paste.pocoo.org/show/200193/
And done! That's my progress so far :) stay tuned for updates.... :P
P.S.
Had to resize the pictures to make them a bit less wide, the actual program is slightly wider than in the above pictures.