You could create a list of your values in a single row, sort that and finally concatenate the values in sorted list together.
Below is one option using associative array
Concat Items(Associative Array(Eval List({:ORIGIN, :DEST})) << Get Keys, "-")
but using something like this should also work nicely
Concat Items(Sort List(Eval List({:ORIGIN, :DEST})), "-")
-Jarmo