I forgot to add that I also need to nest it with a lookup as well (that is what the field is currently set to do).
You can't use both, so use Lookup() function in "calculated value"
Substitute ( Case ( Self = "" ; Lookup ( someYour::field ) ; Self ) ; "'" ; "in." )
You can't "re-lookup" for this field, instead remove value and save it will do it.
Then, if you need empty the field, some more function is needed.