I have created a mail merge record that I want secured as a template.
Different users may open the template in 'read only' and then 'save as' so
they may then enter their personal data for merging with a standard form
letter.

I have the form letter protected and it will allow opening as 'read only'
and then be used by the individual

When 'save as' the mail merge record the protection goes with it and will
not allow the individual to enter their data in the new file.