conditionally show/ hide detail table links

I have a project with mutiple similar detail tables connected to a master. For any given record, only one table will ever be used. I'm tring to only show the appropriate table link based off of a field value n the master table, and I thought that this 10 year old entry from Tips and Tricks addressed this case perfectly. But I can't get it to have any effect. Should this still work on 10.91;,or am I doing something wrong? I tried the simplest example below before setting up a case statement. It's in the List Page: After Record Processed event. The test detail table is named "repair_rf_amp". Any suggestions appreciated. Thanks.