IMO - unless you want to study cryptology
i would suggest using another tested/more secure cipher, maybe something like DES/Blowfish/et cetera... but if this is just for fun/education then ->

(http://www.fortunecity.com/skyscrape...79/lesson1.htm a link i found on AO about cryptology, it's a pretty good read)

i also found this Archive of popular/secure cipher class modules for Visual Basic-> http://packetstorm.linuxsecurity.com...BCrypto_v2.zip