I've got a fairly simple db with only 4 tables. Only two are linked
by a field called E58# with a one to many relationship. In the
"many" table I want to allow a field's (Item#) value for each record
to contain a number 1, 2, or 3 and not duplicate the number under the
same E58# when entering data with a form.

However, in table design when I give it an index of 'Yes, no
duplicates' I cannot enter another Item# 1 or 2 or 3 in a different
record with a different E58#. I only want to restrict duplicity when
the E58# is the same. How can I do this?

I've tried making multiple keyed fields using both fields but if in
error a person enters the duplicate field value it is quite difficult
to extract yourself from the error. Even deleting the record in error
retrurns a message about no null values in key fields.