Question about avoiding duplicated charging
I have made a simple database called "Payables" which help me tracking all the bills that I have paid.
I used to record both my invoice & vender's bill number in each bill that I paid.
Recently, I encountered an issue with my freight vender who double charged me in two different bills.
I'm wondering if there a way to notify me when a bill contains invoices that have charged previously?
For example, in the attached image, a bill no. 021312493 was billed to me based on the 5 invoices indicated in the "invoice no" field. Is it possible to lift a notification in the future, when same invoice number is entered in the same field? This way I can help me avoiding duplicated charging from my venders.