As AgentM pointer out Filter is the best way to go there is a an excellent article in TPJ, Volume 3, Number 3(#11) Fall 98, on how to use the Filter class.

To those who believe this is swimming against the popular tide I say 'Hockey Pucks'.

We often use Rot13 or XORbit7 to protect our code. We do this so that code we have guaranteed cannot be easily tampered with.

The customer still gets source code, but as separate distribution from production code.

mitd -- Made in the Dark
'My favourite colour appears to be grey.'