I have a Person Group type site column that I am using in a custom list through content types. On the Validation Settings page of the list I cannot find that column listed in the selection list of other columns. Therefore I cannot use it in the validation formula. I tried to type it in the formula and got an error.
One or more column references are not allowed, because the columns are defined as a data type that is not supported in formulas.
How can I use a Person Group type column in the validation?