I did something similar. When user opened db, a query written in code looked for qualifying records. If the record count was zero it did nothing. If not, it presented a message box with the count and let them proceed. If you want to do more than that, you could open a recordset and if its count >0 then use it to base the opening form upon. That's just one of many (no doubt) approaches you could take.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.