Field Validation Unique with 1 exception

[Flynn]

I am trying to setup a field where each value is unique except for one instance.

Example A number field where each record would have a unique entry except when entering the number 10 which could have multiple records.

[comment]

You could set up another field with auto-entered calculation (replacing existing value) =

Case ( Numberfield ≠ 10 ; Numberfield )

and validate for unique values in the new field.

However:

1. Validation will occur only when the record is committed;

2. The very need for this suggest there's something wrong with your data structure.