@Michael_EVB Here you go. In cell A1, I have a reference to an external workbook that's open. In cell B1, I have INDIRECT("'"&A1), which returns the value in the external workbook. If you close the source workbook, then the function will return a #REF! error, which is why you need to use INDIRECT.EXT from the add-in. If the source workbook will always be open alongside the destination, then no problem.
The "'" part of the formula is to add back the apostrophe that should be at the beginning of the file path. It is there in cell A1, but Excel sees it as a non-printing character.
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Michael_EVB (New Contributor)