Can you determine if a sheet is password protected before

Can you determine if a sheet is password protected before
opening in Excel.

I presume that you mean Workbook rather than Sheet, and I have never seen or heard of a way of checking prior to opening it. Trying to write code to do this would be extremely complex, so I would recommend looking into other solutions to your situation.

Once you have a workbook open there are methods for checking if sheets have password protection or not.