Excel picks this setting up from the first workbook you open in that session.

So if you always open one of your workbooks first (in A1 reference style), then
open the other workbook(s), you should be ok.

Maybe you could create a "master" workbook that includes a bunch of hyperlinks
to commonly used files.

Then always open your workbook first.  Then open (via the hyperlink???) the
other workbooks.