The find and replace tool that Greg has pointed you at is by far the easiest way to do this. Hopefully you can get that working.

As a learning exercise, read carefully the thread that Macropod pointed you at, paying careful attention to the evolution of the requirements and how that changed the code. Copy the separate code blocks and step through the code each time to learn how it works and what each loop is progressing through.

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Andrew Lockton
Chrysalis Design, Melbourne Australia