Re: Static Worksheet Reference
Short Answer: Always have all the workbooks open when you edit the formulas and Excel will update correctly. Save all the workbooks.
A Better Answer:
Don't name the files with the year number. Use the directory structure to handle the year. That way the files don't need to be updated and maybe not even the formulas. Each new year you just copy the old directory to the new year like "C:\Data\1995" to "C:\Data\1996". When you open the 1996 files, Excel will automatically look in the folder the files are in to update the links.
If you have to update formula with the year to reference the older folder, use search and replace in the summary workbook.