Originally Posted by
p45cal
See DVs in cells B9:C10
In the Distinct sheet, column B I've used TRANSPOSE which makes it easier to copy down the data validation cells on Sheet1 and the formulae on the Distinct sheet; you don't have to do this.
When you've got values in a given row for both columns B & C the validation lists will be mutually compatible; the only way to see a full list again is to delete the other value in the same row.
It is a shame we can't easily use table structured references directly in DV.