Hi,
thanks for your question.
No, this is not possible, unfortunately, as the textareas on the "Edit" screen of TablePress are treated separately by all browsers :-( So, there's no way of connecting them. Sorry :-(
However, if you already have an Excel table, why don't you just import that into TablePress? What I mean: Just prepare your table data in Excel, save as a CSV file and import that into TablePress. If you have many copy&paste operations, that should save you a lot of time.
Regards,
Tobias