Combo box to add records to compound-key table

[Darrell]

I have a main form and a subform where the subform's
record source table has a compound key and is joined to
the main form through a junction table. I need the user
to be able to select a record from the subtable to add to
the junction table with a combo box. The problem arises
when I concatenate the compound key to populate the combo
box. If I make the combo box unbound and populate the key
fields through hidden textboxes on the subform with 0-
width columns in the combo box, the combo box holds the
most recently updated value regardless of which record in
the subform is current. If I bind the combo box to the
concatenation of the key fields, the underlying table
cannot be updated.

Graphically:
With combo box UNBOUND:
Main Form
Subform
record1:cbovalue 1; 1stsubfrmfield1;
2ndsubfrmfield1...
record2:cbovalue 1; 1stsubfrmfield2;
2ndsubfrmfield2...
record3:cbovalue 1; 1stsubfrmfield3;
2ndsubfrmfield3...
record4:cbovalue 1; 1stsubfrmfield4;
2ndsubfrmfield4...
Able to add subform records.

With combo box BOUND to concatenated expression:
Main Form
Subform
record1:cbovalue 1; 1stsubfrmfield1;
2ndsubfrmfield1...
record2:cbovalue 2; 1stsubfrmfield2;
2ndsubfrmfield2...
record3:cbovalue 3; 1stsubfrmfield3;
2ndsubfrmfield3...
record4:cbovalue 4; 1stsubfrmfield4;
2ndsubfrmfield4...
Unable to add subform records.

If this question is understandable, any help would be
appreciated. Thanks!

Darrell