Shared File

Is the file on a shared server? We have that problem all the time. The file is on a shared server used by everybody in the company. If one person has it open and another tries to open it, they can open it as "read only" and cannot make changes to the workbook. Two people cannot edit one workbook at the same time. Once the person who first opened it is finished and closes the file, the second person can reopen the file and edit at will.
Hope this helps,
DaK

Re: also

However, an error message came up and said "the file was in use" and identified a person's name -- someone who did not have it open.

Whoever the computer is assigned to will usually be the name on the file when you get the message. If Joe Schmo is using the file but on Jane Schmo's computer, it will say Jane is using the file. At least thats how it works here.

DaK

Actually you can share a workbook that allows others to edit all at the same time if you want to....you just have to save the workbook in share status.
tool/shareworkbook
that is the way we do it here at my work so we can have the workbook open at the same time.