Modify forms based on criteria

Hi, I'm trying to figure out how to code a procedure to show a control as "visible" on select forms, based on entering a number on the current form. Specificly, I use control numbers to track equipment modifications. When the equipment needs to be revised, the same control number is used, but an "R*" is added to the end where * is the number of the revision. All previous records must be kept, each with their control numbers (04-123, 04-123R1, 04-123R2, etc) and I want to cause a normally non-visible label on all forms related to the Revised control number to show as visible. The label is simply a statement in red that states "the modification has been revised, refer to the most recent document." When an entry is made, the code needs to look at the control number and set the label property to visible on all related numbers. I hope this isn't too confusing, I've wracked my brain on this one. Thanks!