A year or two ago, while browsing a Sydney bulletin board, I came across a little program that claimed to be able to crack passwords on WordPerfect 5.1 files. (I mention this only because some computer users mistakenly believe that password-protected files are always invulnerable). It wouldn't surprise me at all if some talented programmer -- long deprived of sunlight and aged about 13 -- hadn't written something similar to break into password-protected Excel files. But I haven't heard of such a program, and if I had, I wouldn't want to publicise it.
Some organisations insist that staff write all their passwords on paper, for storage in the company safe. This is perhaps the best way to ensure that legitimate users are not denied access to vital data in situations like the one you describe.
- Neville Clarkson