JoAnn Paules [MSFT MVP] wrote...
And since the file was protected in the first place, maybe you shouldn't be
trying to break into it.
....

Then again if the file was created by person A at work, legally the
file would belong to A's employer. If A quit or was fired and is unable
or unwilling to give the password, and if the OP works for A's former
employer, the OP would have the legal right to crack the password.

That's the most common scenario claimed by people asking how to open
password-protected Excel workbooks, at least in the Excel newsgroups.
If it weren't legal to crack some files, it's hard to imagine why the
people providing the service for a fee aren't all in prison by now.