Dynamic workbook reference

The gist of this formula is to build up a complete reference to a range in another workbook as text, then use the INDIRECT function to convert the text to an actual reference.

A reference to an external worksheet looks like this:

'[sample data.xlsx]Sheet1'!A1

Note the square brackets ([ ]) around workbook name, single quotes (' ') around the worksheet + sheet, and the exclamation mark (!) that follows.

To create a reference like this using text, we use concatenation to join values from columns B, C, and D with the required brackets, quotes, and exclamation mark:

=INDIRECT("'["&B6&"]"&C6&"'!"&D6)

The result is fed into INDIRECT as the ref_text:

=INDIRECT("'[sample data.xlsx]Sheet1'!A1")

The INDIRECT function then evaluates the text and converts it to a reference. Excel follows the reference and returns the value at the given reference.

Note: if the reference is invalid, or if the workbook referenced is not open, INDIRECT will throw a #REF error. You can catch this error with the IFERROR function and display a custom result if you like.