Lowell's told you how to do it. If you want a script run once off to encrypt all procedures, write one up that does what he said.
Why are you going this route anyway? You do know just how easy that 'encryption' is to reverse?
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability