I just started using Excel about a year ago, and have had no training, so
please forgive me if I appear somewhat dense.  I may not have explained the
problem correctly and/or I may not be understanding what you're telling me.
Please bear with my attempt to be clearer and more specific:
- I created a workbook on a separate drive.
- I hid the duplicates.  I sorted the data.
- I checked the box to share the workbook.
- I saved it.
- My co-worker accessed the workbook.
- What he saw was exactly what I saw: duplicates hidden, and data sorted.
- He color-filled a row.
- He saved it.  So far, no other changes appeared in his view.
- I saved the workbook on my end.  I saw his color-filled row.
- I ALSO saw that the duplicates had re-appeared and that the data had
become un-sorted.
- On his end, at that point, the duplicates were still hidden and the data
still sorted.
- But when he saved his workbook again, he was looking at what I was looking
at, i.e. duplicates reappeared and data un-sorted.

If I understand you correctly, it would seem that for the duplicates to stay
hidden and that for the data to remain sorted, the solution is to UN-check
the box for Filter settings on the Advanced tab of the Share Workbook
option?
Somehow, that seems a little counter-intuitive to me, but I'm looking
forward to trying that out at work on Monday --- hope it works.
Thanks for your help, Debra, and please let me know if I've totally
misunderstood your solution.

-- Alan