Depends on a few things,
I think this is what your wanting to do.
If they are setup as 3 separate parts with 3 separate work pieces as shown below.
Then under job assignment you assign operations to each part in the order you want them done "marked 1,2,3"
Attachment 254438
This also works if you are milling many different types of parts and sizes in the same setup. or parts that become fixtures later on in program in the same setup also.
Job assignment order in this case has one level of control.
md
oops I re-read your text and it says bar of material, that's different