So what you really want is a way to randomize the values in your test system? This is an entirely different situation than encrypting data in a column. Of course all you are really going to do here is to change the value of the account number. This would be really simple to do. Just create a quick and easy algorithm to take the existing value and turn it into something different. Then update all of your tables using the same algorithm.

Also, you mentioned twice about developing cursors and you throw that out there like it is something you do frequently. Cursors and other forms of looping in sql server is probably the absolute worst thing you can do for performance. There are times that they are needed but those are generally left to administrative tasks and NOT something that you need in every day sql programming. Next time you are about to create a cursor, instead start a new thread on SSC and we will help you figure out how to perform the same thing a LOT faster.