I would like to use the track changes function on a file that is shared, what
we have been doing in the past is changing the name of the doc to reflect the
newest version. eg. "workbook20060901." If we were to use the track changes
function, the file name would have to stay the same?

Any suggestions on how to make certain that we are always using the newest
version?

I don't see why those two events- making datestamped copies and using
track changes- would have to be mutually exclusive events. It's
understood that the later version of a file will have more data or
updated data; track changes simply tells who did what to whom and when.

You can make sure the team is always using the latest version of the
file by saving older files to a sub-directory Archive and saving the
current file to a subdirectory called Current. I do something similar
via code to save a version that includes both a date- and time-stamp so
I can differentiate between multiple changes to files made on the same
day.