Am using a nested continuous bound subform to add multiple records to the
underlying table. One of the fields is based on a limit to list combo box.
Any suggestions on best way to progressively update the combo box query so
that for each new record being entered the combo box list excludes items in
the combo box list previously selected.

Aim is to prevent user from selecting the same combo list item more than
once if the user has already added a record previously using that list item.

The combo box field is part of the primary key for the underlying table and
am currently trapping the duplication error and then getting the user to
re-select a different combo box list item but would prefer removing the
previously selected & saved combo list item from the pick list.

This would allow me to also include logic to exclude mutually exclusive
items as well from the pick list.

Example in summary.

Combo box initial pick list items
A
B
C
D

To Avoid duplication - if user picks B and record is then saved, pick list
for the next record on the continuous subform becomes
A
C
D
For Mutually exclusive items - want say A & C to be mutually exclusive - if
user picks C and record is saved, pick list for the next record becomes
D

Any suggestions on best way to handle updating the selection criteria string
appreciated.

TIA, Bob