here is a work around, as I'm not sure of the correct answer.
create a part model. create two datum points, using the sketch method, then put a dimension in the sketch, value is not important.
then in your drawing, show a view of the part. Show/Erase the dimesion. put the points on a blanked layer so you don't see them. then, modify the dim, change the symbol to X & changed the syntax to @O (instead of @D)