I have an inventory with Items in Stock and Items Sold.
I created a field called Items Remaining that is validated by this calculation "Items in Stock - Items Sold"
The system works fine but I would like to put a condition that when you insert new "Items Sold" and the number is bigger than the "Items Remaining" you will get an alert saying you're overbooking.
Now "Items in Stock", "Items Sold" and "Remaining Items" are in the same Inventory table
Entering new Items Sold is on a Sales table and the 2 table are unrelated.