First of all, I don’t think the title of your thread is very helpful. Maybe this is food/drink terminology that I don’t understand, but to have the best chance of reciving relevant assistance, I would suggest changing it to “track individual customer spending” or something like that.
With regards to your query, take a look at customer accounts and miscellaneous products
One type of entity can be a customer
and a customer can have an account assigned to them. This is a special type of account that although can be shown in the regular accounts section within SambaPOS the account is also directly linked to a customer (who has a name, phone number, address, whatever you like).
By setting up the correct Account Transaction Documents you can process a payment through the accounts screen. This is where you would accept the $1000 in to the till and credit the $1000 to the customer account.
Now, once the customer has the $1000 credit with you, you can open a ticket and assign the customer to the ticket. At the top of the ticket you will see the customers’ current balance. You can add a round of drinks to the ticket and then settle the ticket. But instead of settling the ticket for cash, instead you will settle it using the “Customer Account”. This will reduce the customers’ balance.
With a good ticket template, you can explain things like “Previous balance, money spent this round, balance remaining”.
If the customer over-spends, great! You can just keep ringing through extra drinks and settling each ticket against the customer account. Eventually the customer account will go through zero (0) and start becoming a debt (again, you can print this on the ticket). By the end of the night the customer will have a series of tickets (a ticket for each round of drinks) and you will be able to tell them how much extra they owe (which you can process through the accounts screens).
If the customer doesn’t over-spend, then you can create one final ticket and add a “miscellaneous product” to the ticket and give it a price equal to remaining balance on the customer account. Settle this very last ticket and then the customer account will equal zero (0). In terms of reporting, you can filter or report on just this one particular miscellaneous product to see how many times you are making money by VIPs under-spending.
Take a look around and you will also see the @QMcKay has also provided a very detailed tutorial on how you can setup a very fancy system particularly geared around customer accounts, this could be something to look in to, but I found it rather daunting when I started out with Samba.