Excel repair for Mac

Help!

My very important budget-file is corrupted! I use Excel for Mac 2008 on my Macbook (Mac OS X 10.6.8). I recently used the file but now when I want to open it it says 'The file you are trying to open is possibly read-only or the location you are trying to open is read-only. Or the server you are trying to access is not responding'.

I'm afraid the file is corrupted 😟

What is strange is that there are two other files which all of the sudden have the same issue, all 3 files have the .xls extension instead of .xlsx which I can open without a problem.

I didn't do anything myself to these files?! So is it a question of corruption of wrong extension? No idea!

I've allready tried searching for a program that can repair corrupted excel-files but they don't work on my Mac, are all for Windows OS.

Can anybody help?? I'm getting really desperaty here! It's a very important budget-file, and ofcourse my back-up with Time Machine is from after when i last used the file 😟 😟

Any help would be MUCH appreciated!