It can be done with formulas, but will require that you not change the location of the files, because you need the path constant. Also, depending on the kind of data you need, you might have to experiment a little.
For instance, you can open both books, and in the target workbook, enter = in the desired cell, then click on the other workbook and the appropriate cell. That should get you started. I don't have Excel any more, but had worked with it every day for 8 years until this year.