Form field: Show all values from a list except the used ones

[Jewel]

We have 2 tables:

• References => Column ‘Reference’ (type “Enum” with many values as references for the quotations)
• Quotations => Column ‘Ref. Quot.’ (type “Ref” pointing to the table )

Problem:
I would like, whenever I fill the form Quotations the Appsheet, in the column “Ref. Quot.” only shows the values (from the column “Reference”, table “References”) which have not been used yet.

I.e.: I have made already several quotations, each with the references

• 202201 ANOA
• 202205 LEOPARD
• 202204 GIRAFFE

Next time I make a new quotation the app
(1) OR must show all the values from the table “References” EXCEPT the values that I already used (202201 ANOA | 202205 LEOPARD | 202204 GIRAFFE).
(2) OR can suggest one (1) value (from all the values of the table “References”) randomly, EXCEPT the values that I already used (202201 ANOA | 202205 LEOPARD | 202204 GIRAFFE).

I have tried and tried to search for a solution but I cannot get it, sorry… Someone can help please…? Thank you so much in advance!