Using "indirect" and "concatenate" to reference across workbooks.

I am attempting to use "concatenate" and "indirect" to reference a cell in a different workbook, but am not having any luck.

In this example, an employee is interested in looking at job "999.123", and thus enters that number into the first cell. The file itself is saved as "999.123.xlsx", so when they enter "999.123" into the first cell, it should combine with the beginning and ending of the file-path listed - I can get it to link when I copy & paste the concatenated value into another cell, but I can't get it to work on its own.

Thanks in advance.