I wanted to do something similar in my database. I wanted it to update 'last active date' in several tables, but not if I was just looking at the records. I have several update queries that run in the background on the 'after update' but only when I key in a specific control. I can key new products and new tickets, but it only runs my update queries after I key in my grand total in the billing. At that time, it updates the drivers that worked on that job (so I can see their last date worked), the last date that product was hauled (so I can eventually purge products no longer used), the supplier (so I can eventually purge suppliers that we no longer use) and the last date the job was worked on (so I can answer my boss when he asks when we last worked on a job).
This is very convenient and it doesn't appear to slow my computer down in a very obvious manner. This might not work for databases that have many users, but we only have two that use it at the same time.