You can just set the form's AllowEdits and AllowDeletions to No. However,
this blocks the use of unbound controls as well (e.g. for if you provide
filter boxes on the form.)
Here's what I use:
Locking bound controls on a form and subforms
at: http://allenbrowne.com/ser-56.html
It locks the bound controls only, and handles subforms recursively if you
need that too.