Accessing Tag Property in a Transaction Group Expression Item

In a Transaction Group, I’m trying to create an Expression Item that evaluates to the value of the Engineering Units for a tag in the group.

I’ve set it up with the expression of {[~]Tag.engUnit}, {[~]Tag/engUnit}, and many other permutations of capitalizing engUnit/EngUnit/etc.

Every time, the expression item just evaluates to the value of Tag, and not its units.

Am I doing something wrong here?