My question is can I limit data entry based on total box field. In other words I can't have more than 4 boxes of 46001 in the [
box in] table at one time?
You have this number before the data entry starts? Then in the BeforeUpdate for the form, check the DCount of this field and cancel the update if the expression return value matches the count value:
DCount("BoxFieldName", "TheTable", "BoxFieldName = " & YourControlNameOnForm)
Downside is that user would have to move off the record to trigger the event. You could perform the validation no matter which control the user enters if you either put the same code on each control BeforeUpdate, or just a line to call a function that you put the expression in. The downside of that would likely mean that you could not edit existing data, so it would require a work around.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.