How do I prevent others from editing my workbook after I've emailed it to them?

I have multiple sheets in a workbook and would like to prevent users from editing and being able to see the formulas contained in the respective sheets.

So far I've tried formatting the cells by selecting the 'Locked' & 'Hidden' options, and then going to Review | Protect Workbook | select 'Structure' & 'Windows'

When I email this protected document to a coworker, they are able to open it, edit and view all formulas?

What am I missing here?

Not sure what is going on in this specific case. However, there is no safe way to protect an Excel workbook.

When you lock and hide formulae, you need to protect the worksheet with a password, not the workbook structure, although that's not a bad idea. Personally, I think that if you just want them to see the data and not change it in my way, the best way is to select all the sheets and save it as a .pdf file.

Regards, TMS

Thanks for the rep.