That was a typo on my part (too many "o"s!). It's safer to point to
everything explicitly I find but, yes, code assumes the active sheet in the
active workbook otherwise.

I don't think you can reference closed workbooks directly with VBA. One way
around this is to open the workbook with code (Workbooks.Open "path to file")
or I suppose you could create linking formulae in an already open sheet and
reference those in your VBA.