Validation in a field with a list of values

Summary:

Can validation be applied so that a field containing a list of values auto-completes with a value based on what is entered in another field?

Example:
Field A has the values 1, 2, and 3. (Field A Property type "Enumeration", GUI "Combobox")
Field B is an integer.

If I enter the value "10" in field B, field A should auto-complete with the value "A."

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