Then when you add an item to your selection list, requery the combo box so that the list will now exclude the item you just added
would just add that you need to do more in a continuous form otherwise previous entries will appear to go blank
So you need to modify the rowsource to exclude previously entered items in the combo enter or perhaps gotfocus event then remove the exclusion on the combo exit of lostfocus event. There is no need to requery the combo as modifying the rowsource does that for you - but just for that single instance on the form. If you were to requery, all rows will appear to go blank.
Also means you would need to manage the situation if the user goes back to change an item (it will no longer be visible in the dropdown).
I would suggest the principle used in this thread would be more appropriate
Thought I would put this up since it is a fairly common topic and I have put it up elsewhere - selecting records from a list for onward processing without the need for a table based tickbox. Similar in concept to the conditional formatting version I provided here...
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The bit that matters is basically when a user enters a value the relevant uniqueID for the product? is checked against the hidden textbox. If it is already there then generate an 'already entered' message and presumably clear the combo, otherwise add it to the textbox
Still needs more work to remove from textbox if user changes the selection and perhaps the textbox needs populating on some event (such as current) if user can edit a previously created issue.
So two methods, one to restrict what users can select, one to create a a message if user chooses an item already chosen