I have tried saving an xls sheet under a different name using a password to
stop others from changing the contents but I can't seem to get it to work.

I go to "File", "Save as", and then click on "Tools" on the "Save As"
dialogue box that comes up.

I choose "General Options" and enter a new password in "Password to Modify"
(I also put a tick in the "Read only recommended" box.

I click okay and another box comes up wanting me to re-enter my password,
which I do and click okay.

I then save the sheet.

Later I load the sheet again and the first thing that happens is I get a
"Password" dialogue box, whixh says "Enter password for write access, or
open read only", so Iclick on the "Read Only" button.

I can then delete and modity whatever, no problem, I want and save it right
on top of the original!

What am I doing wrong, please?