Need method to validate if user has rights to change cell contents

Hi Everyone -

I have a spreadsheet that I want everyone to be able to look at but only certain individuals can change the cell contents.

I do a check when a user first opens the spreadsheet to see who the user is and then look up the user in a table to determine their rights, ex John Doe can VIEW, Mary Jane can EDIT.

Option 1:
I want to set up an trap that checks whether the user has EDIT rights, and if so, allow the change to the cell contents. If the user does not have EDIT rights, I will display a message telling the user that they do not have rights to edit the cell content.

Do I need to check via Worksheet_SelectionChange after the fact or is there a way to make the check when a cell is first selected?

Option 2:
Make the spreadsheet read-only when first activated, then check if user has proper rights to EDIT. If so, then set the spreadsheet to Read/Write. This would seem to be the simpler way but I have no clue how to set it up other than protecting the speadsheet.

Thanks in advance for any help!

Jim