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First I set a local variable which is the value that will be applied to Prop:Timer. There are two places this happens (as you'll see); I use a local variable so that if I want to change the value I only need to do so in one place. A value of 50 means the timer will execute every half second, which is probably a lot less frequent than I'd really want it to happen but it allows the process to execute at a good demonstration speed. I'll also only be processing on one record per timer event.
I then do a Set in primary key order on the People file.
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And of course this was a one-off job; if I come across other places where I need something similar I'll look into creating a class and/or a template. But sometimes a little hand code goes a long way.