04-25-2011 06:04 PM
I just did a quick test with the Playbook. I created to Excel files in the Playbook documents folder. Test1.xlsx just has a couple of numbers in it. Test2.xlsx references the two cells in Test1.xlsx and then sums them up. Test2.xlsx just has =#REF! where the references to Test1.xlsx were.
It seems like you can only have one spreadsheet open at a time too.