Convert from letter to int

1

hey.
how would i convert a letter to its corresponding utf integer and back to a letter?
Trying to do a real simple rot encryption
[AS]
private function decrypt(line) {
var line = line.split("");
trace(line);
for (var zz:int = 0; zz < line.length; zz++) {
line[zz] = ConvertToUTF(ConvertToInt(line[zz]) - offset) ;
}
trace(line);
}
[/AS]
ConvertToUTF(); should take in a number and convert it to its corresponding letter
ConvertToInt(); should take in a letter and convert it to its corresponding int

Thanks!

P.S. im not sure that its called utf, but i mean how every letter corresponds to an integer.
in java i would do like this

 e[x] = (char) ((int) e[x] - encryptionOffset);