Here is my thought, having now seen your description of your workflow. First, just some advice. Calling out front-end and back-end users is very confusing nomenclature to us because those two terms have highly specific meanings to us that are not consistent with your description.
ALL repeat ALL of your users should only use a front-end file to use the app and the back-end file should NEVER be directly addressed. There is a serious danger of file locking issues leading to file corruption if you actually DID have a direct back-end user sharing with front-end users.
I believe what you call "front-end" is the front-end of your process and the "back-end" is just a later step in that same process. And if that is a correct interpretation, then what you have been saying makes a lot more sense, just involving misleading terms. If you actually meant front-end and back-end in the same way that we normally use them, you need to reconsider.
Now, regarding that notification that something has been added... You really don't care about what you asked. (Hear me out...)
Let's say that you have a small bunch of people entering data in the entry phase of your process. You have one person (from your description) that does validation. But which of those activities is really and truly time-critical? How often does it happen that the validation person catches up with the inputs of the data entry people? And if a new entry came in, would the validator stop the current validation immediately? Or would the validator finish that entry and move on to the next one?
I'm thinking that if you put a .Requery in the validation form's Form_AfterUpdate event (i.e. after the validator makes some entry that says "OK" and is then done with the entry), the validator would go on smoothly to the next request. Because at that point, the old record would have been updated but until you release that event, navigation and the "Current" event can't occur.
IF it happens that the validator CAN catch up, then the rest of the solution is to put a timer on the form the validator would use, but this timer would cycle ONLY if the validator has not yet "taken" one of these new records for examination.
I hope I said that clearly enough that I didn't confuse you.
EDIT: You posted just as I finished composing this. IF your multiple users are sharing database A as a non-split database, you STILL risk issues of file locking leading to terrible corruption. And if database B is a separate non-split database, again you have multiple users sharing a file with someone who is local to that DB, and that again can lead to issues.
