I've learned that Indirect only works in referencing another workbook
when that workbook is open.
Is there a way to have a list of references to external workbooks that
can be selected from a validated list that would then reference a
closed workbook?

I know how to create the validated list.....
Its a matter of finding an alternative to Indirect that would allow me
to reference a particular workbooks cell value.

For instance

Suppose the list was something like
[workbook1.xls]worksheet1'!A1
[workbook2.xls]worksheet1'!A1
etc.