Copy Unique Items to a Array

Is it possible to store unique items from a list into an array, then populate a cell data validation list with the unique items array??

Here is the code to set up the data validation. I'd like to be able to replace "test, test1, test2, etc." with the unique values from my list.

With Range("O2").Validation
        .Delete
        .Add Type:=xlValidateList, AlertStyle:=xlValidAlertStop, Operator:= _
        xlBetween, Formula1:="test,test1,test2,test3,test4"
        .IgnoreBlank = True
        .InCellDropdown = True
        .ShowInput = True
        .ShowError = True
    End With