do you mean the rot 13 algorithm
because you could just use a value of each letter and do something like the following
function cipher(value as integer,key2 as integer,restrict as integer)
//cipher = Mod((value + key2),restrict)
cipher = value + key2
if (value + key2) > restrict
cipher = mod((value + key2),restrict)
endif
endfunction cipher
function deCipher(value as integer,key2 as integer,restrict as integer)
//cipher = Mod((value + key2),restrict)
deCipher = value - key2
if (value - key2) < 0
deCipher = deCipher+restrict
endif
endfunction decipher