Hi Nancy,
Unfortunately, what you're looking to do through the Import/Export tool isn't possible out of the box. You could customize your Method screens to automatically update your customer records with the changed rep. I'll explain.
When you are importing or updating a table in Method, you are only updating that table. In your case, this is the SalesReceipt table. There is no backend logic in Method that would detect that a record got changed and then update a value in another table. Also, if this was the case, you might run into issues if for instance only 1 out of a customer's 8 sales receipts was changed. Which record would trump which? The old sales receipt that was just updated, or the latest one?
Also understand that QuickBooks offers a choice to reassign the customer's sales rep. This isn't done automatically (at least not right away). It requires input from the user to confirm that they wish to modify the customer's sales rep.
You can certainly customize Method to do the same. I realize you want to mass update records, so for your scenario, you could also customize a screen that loops through the SalesReceipt table and updates the Customer table, SalesRep field with the value from the SalesReceipt table, SalesRep field. In simple terms, the button would loop through your sales receipts and update the sales rep field in the customer table.
If you haven't done any customization before, I'd highly suggest going through our Customization Webinars. They should give you a better understanding of what needs to be done. A project like this can have a varied range of difficulty depending on the logic needed. If you wish to work with a consultant on this, please have a look at our consulting options.
Hope this helps,
- Adam