Index formula while working with different workbooks

I am retrieving values from several different workbooks and their sheets with index formula instead of indirect and address because of closed workbooks. However, file names change every month (for instance; bla_bla_Jan.xlsx to bla_bla_Feb.xlsx). If I break the links and change them every month, does it affect current values gathered with index formula? Or is there any other flexible method to lookup workbook names and sheets by month names only while keeping current values? Thanks in advance.