List Boxes And Combo Boxes

Hi everyone,
I have been making progress with customizing a
MS Access program, but one major problem is that
I have been trying to make a List Box or Combo Box
that I can use to enter data in the TABLE, but I
find that I get a pull-down list that has the list of
values from only the parameter that is primary key.
More specifically, the program is set up as follows:
I have two tables in this program: One that is called
"invoices" and one that is called "items". In both of
these tables, there is one common parameter, which
is "Item Number". Item number is the primary key,
and I used the "relationships" function to tie this
parameter to itself between the two tables.
I was successful in setting up a list-box for the
"Item Number", but when I try to set up a list-box
for another parameter that is supposed to display
a person's initials, the pull-down list displays the list
of item numbers instead of the list of people's initials.
In fact, I don't know if there is an extra step I need to
take so that the database stores a list of people's initials.
Instead, I just fill in the initials in the field for each
record for which the "Item Number" is the primary key.
How can I get the list-box to pull down a selection of
different people's initials, or in other words how can I get
all the people's initials to be stored so that the list of
initials can be looked up. Just so you know, I have tried
different choices of entries in the "Lookup" tab in the
Design mode of Tables, including Display Control,
Row Source Type, Row Source, and Bound Column,
but the outcome is that the only parameter that I
get get in the pull-down list is the primary key, which
is Item Number.
I appreciate any help you can offer in explaining how
to correct this.
On a separate note, one of the parameters is "Date", and
on the reports, I'm trying to figure out how to filter a
specific date range so that I can limit each report to a
specific month. Please advise me on this procedure as well.
Thanks.