I´m using this to check if the code is already used:In the Valid If of Data Validity I placed this:NOT(IN([Audienciaunica], SELECT(Audiencia[Audienciaunica], [ID Audiencia] <> [_ThisRow].[ID Audiencia])))I was thinking if there is a way to check this...

Any combination is acceptable. I was thinking on consecutive because sometimes it helps in unique verifications. You have to reach the end of the combinations for a possibility to have a duplicate.

You´re right. I´ll use this as a solution. Thanks!Just to left a note about this:The only problem about this is that UNIQUEID() generates a random sequence, not an unique one. And the possibilities of getting an unique code are 100% when using 8 posi...

Thanks! but will this include all letters or just HEX?

Hello, thanks for your answer. I read a lot more about this and this drive me to the solution:FILTER(Geo,[Proyecto]=[_THISROW].[Proyecto])This is placed in the valid_if and it brings me the list filtered of Geo that belongs to a specific project.I un...