First, nothing is automatic. Not even a car's engine. While you may not shift the gears, some action is causing the transmission to do it.
So, what would you like to trigger this APPEND query?
Second, 95% of the APPEND query questions on this forum are not the real issue the person is having. The real issue turns out to be an improperly structured database. So, can you explain why you need to APPEND data? And why it has to be "automatic"? Is the valuue some sort of total of other data?