One work-around will create the result you are looking for. The workflow might be a little cumbersome though.
The idea is to create a balloon and a note and group them together. Then copy and paste multiple times for all the parts.
Create a balloon with the default "Item Number" data. Next create a note, attach the leader to the same part as the balloon, select "Link to Property", select "Component to which the annotation is attached, select "Number" or other appropriate custom property of the part from the drop down. Next, hide the leader, move the note adjacent to the balloon, Ctrl-Select both and group.
You now have your item number and part number associated with a particular part.
Again, ctrl-select both the balloon and the note (even though single clicking shows it gets both items in the group), copy with ctrl-c, select another part edge / face, and paste with ctrl-v. Both the balloon and note will grab properties from the selected item.
For some reason in my SW2012 SP5, if I single click the group when I copy I only get the note when I paste - hence the ctrl-select of both items noted above. Also, when I paste the grouped items, the note does not remain tied to the balloon in the proper location. It will require some additional placement editing which can be done by just dragging without ungrouping. But once positioned correctly the two grouped items move together when you click and drag the balloon.
Hopefully someone else has a smoother process.
Presumably you have solved this by now, but there is an easier way to generate the note.
Create a note with attach the leader to the required component, and select "Link to Property" (As Daen stated), select "Component to which the annotation is attached, select "Number" or other appropriate custom property of the part from the drop down.
Place the text and click away or ESC. Right-Hand click on the text and select "Edit Text in Window".
Copy and paste the text within this window, and add as many custom properties or standard text as you like.
The underscores are just there for our filing system. They could be any text.