Duplicates in a multi-select text fiel

I have two multi-select text (summary) fields in my table "customer orders" which show several customs tariff no. 4819.10, 7307.29 etc from the related child records "ordered products" and "ordered tools". I would like to bring the results of both multi-select text (summary) together in one formula-text field by avoiding any duplicates in the results.

Currently, I have the following formula: ToText([FieldA]&"; "&[FieldB])

This formula list all customs tariff no. but how can I get rid of the duplicates in case there are some?

Thank you for your support.

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Tom
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