Is it possible to create a spreadsheet that auto generates a sequence number every time the spreadsheet is opened, or, for example, a button is pressed.

The sequence should have a certain prefix, for example DK-XXXXX-followed by the sequence number, and the user should not be able to overwrite the fields, at least not the output. Finally, the spreadsheet should automatically save the spreadsheet upon exit, so avoid the risk of using the same sequence number more than once.

Is all this possible?