Jim is correct, there is no way to be 100% certain that your work can’t be
hacked, stolen, etc. However, I’ve found that the following combination
(both #1 & #2 together) offers pretty good protection:
#1) Tools > Protection > Protect Sheet (or Protect Workbook), then enter a
Password.
#2) Tools > Share Workbook > Allow Changes.
When you say 'sharing' I can't tell if you mean you will do a 'Share
Workbook', like I described above, or whether you will simply distribute your
workbook to other users, but if you do en up doing a 'Share Workbook', be
forewarned that several users in the file at the same time will probably
corrupt the file. It depends on the size of the file, I believe. If you
really want to share your data with other users simultaneously, and in real
time, you may be much better off using Access for your app, or you may be
much, much, much better off using Access for your app.
Good luck,
Ryan---