As Jerry said the user security is a bit complicated and a pain. However, a
shortcut would be to disable the form after update so in otherwords, have the
form open to a new record on open. After the user enters the data and clicks
the Add Record button the form will disable so when you scroll back to
previous records they are locked and cannot be updated. You will want to put
a password field and button on the form so ONLY those people who have edit
rights can enter the password, click the password button and enable the form
for editing.
What's unfortunate is I can't seem to find the database I had the code in
because I had one set up like that and worked great. But at least the idea is
there and if you do a search in this forum for Disable and Enable fields,
password field, password button and so forth you will probably find what you
need. If I come across that database, I send you the code and how to set it
up.
Hope this helps!!