Protecting worksheet vs workbook

I think we're talking about two different issues (or I'm being very stupid!)

I already allow users to type into the protected worksheets by having the designated cells as 'unlocked'. I just tried the 'allow users to edit range' option out of interest and couldn't get it to work anyway?

The issue is that I want to prevent the users from being able to delete one worksheet but not be prevented from deleting the others - protecting the sheet does not affect this and protecting the workbook disables the delete option for all the worksheets. I'm wondering if it has to be some VB code to activate/deactivate the protection dynamically or some such.

Attached an example.

The 'do not delete' worksheet - I want it so it is impossible to delete this worksheet but you can still delete the data entry worksheet (or add new ones). Both worksheets are protected, but you can still add data to the data entry sheet.