Sounds like you are still confused.  A ComboBox is NOT used to change any of
the data you see within the rows of the ComboBox.  It is a resource for the
user to enter a value on your form.  In that regard it's the same as a
TextBox.  However; it provides two things that a TextBox does not.

1) It can simplify or speed up entry by offering a list of choices rather
than forcing the user to type out all of the characters.

2) It can restrict entries to only those provided in the list when the
property LimitToList is enabled.

Now, there is a special case.  You can have a form bound to your table with
the two fields and you can use that form to edit none, one, or both fields
simply by enabling the locked property on the control(s) you do not want the
user changing.

To make it easy to find the record in your table that the user wants to edit
you can add a ComboBox that is used to *navigate* to the appropriate record.
In this capacity the ComboBox will use the same table as its RowSource as
your form is using, but its ONLY purpose is as a navigation tool.  It plays
no role in the editing of the record the user is taken to.  That would be
done by using other *bound* controls that you have on the form.  The
navigation ComboBox would be unbound (blank ControlSource).

If this is what you want the ComboBox for then first build your form that
allows you to edit your data.  Once that is built then add the ComboBox
making sure that the toolbox Wizard is turned on.  One of the choices for
the ComboBox wizard will build exactly the ComboBox you need.

The combo has a number of interrelated properties. This one is the Bound
Column. See below...

RowSource: a Query which retrives from one to ten (I think more are allowed in
recent versions) fields from a table (or from joined tables); some fields can
be calculated fields if that's appropriate.

ColumnCount: How many of those columns are included in the combo box itself.

ColumnWidths: a string of numbers, as many as ColumnCount, separated by
semicolons; each number is the width in inches or centimeters of the
corresponding column. Zero width columns are invisible when the combo is
dropped down; only the first nonzero width column is visible when the combo is
not dropped down.

BoundColumn: Which column will contain the Value of the combo box.

Control Source: which field in the Form's Recordsource will receive the
selected value. May be blank.

For example, you might have a query

SELECT PersonID, LastName & ", " & FirstName, Position, DOB
FROM Personnel
ORDER BY LastName, FirstName;

Thiss query would return records like

312; "Aarons, Michael"; "Researcher"; 3/2/1955
506; "Able, Janet"; "VP Marketing"; 5/10/1950
229; "Acton, Bill"; "Custodian"; 11/20/1946

This query might be used as the Rowsource of a combo box cboPersonnel. Set its
ColumnCount to 4 and its  ColumnWidths property to

0";1.25";0.75";0.5"

and you'll see only the (calculated field) full name displayed when the combo
is not in use, but (for identification purposes if you have duplicate names)
the person's position and date of birth when it's dropped down.

Set the Bound Column to 1 and it will store the PersonID into a PersonID
foreign key field in the form's recordource (if its Control Source is PersonID
or the corresponding field in that table). If the Control Source is blank, you
can put (or let the wizard put) VBA code in the combo's AfterUpdate event to
navigate to that record, or to do something else with that PersonID.