How to sort related records

[HCF]

I am tying to sort related records to my Contacts table on a column from a referenced table, but as the editor can’t find the column, I am stuck. I wanted to do something along these lines:
OrderBy(
select(Activities[Contacts],
in([_thisrow].[UniqueID], [Contacts])
),
[SortColumn]
)

Thanks for any help.