>Now I also want to add Valid Code,When code at runtime ,probably from a memo field on the user defined table, and am wondering whats the best way of doing this.

You can't do that. But what you can do is create a set of column classes that already have your valid code in them, and decide at runtime which class you want to use.

Or, you could write your valid code in a set of functions and have a single column class that decides which function to call dynamically, and calls that function with EVAL(), returning the result.