How to calculate a field based on other "found" records
2 Tables - Main , Cart
Main::ID = Cart::ID
This is in a "store front" format for the web. User Creates Main::ID record, chooses item which adds a new record in Cart that is linked to Main. I have a field Cart::Item_ID that i want to calculate the ID based off of Main::ID & How many records there are for Main::ID..
Main::ID = PSOL100 then Cart::item_ID = PSOL100-1 or PSOL100-2 if a record PSOL100-1 exists.
This would then start over at -1 for the next Main::ID record
So then the Invoice would show a Main::ID with sub records of Cart::item_ID which will then be barcodes for tracking throughout company.
Any thoughts, Questions...I'm horrible at explaining so bare with me..