VB.NET encryption/decryption

Using the following characters ONLY

abcdefghijklmopqrstuvwxyz
ABCDEFGHIJKLMNOPQRSTUVWXYZ
0123456789
~!@#$%^&()_+`-=[];',.{}

I need a decent algorithm to encrypt a textbox string which holds a file name and extension that must not be readable by human eyes i.e.

"File.txt"

"Gd7&.@0x"

I also have a textbox where the user can set a password so that the filename and extension can also be decrypted back to the original file name.

Offers and time required please.

Have you tried searching the forums on how to do it?

I don't have the time to search around and look for it and then to make sure it all works etc, I've got a lot to do at the moment which is why I would like a quick bang thank you mam solution to it...