Link to cell in closed book with a variable sheet.

Hello there.

Would you please help me with my issue?

I have a file with 50 sheets and every sheet has unique name (8 digits)
There is another file and I want to make a link to the cell in that file
Here is a problem
I need a formula in my file like this
='\\there is a path to file\[FileName.xlsx]SheetName'!A1
but this SheetName I need to get from a cell in this file wich is located in lets say cell G2
so I need something like this ='\\there is a path to file\[FileName.xlsx]G2'!A1 where G2 means cell that has 8 digits like my real sheet names
of course I need formula that will be copied to any files and get data from closed file

Thank you in advance!