How can I get the "not" of a list of values in an RTC Work Item

Hello,

I have a list of values (appearing as checkboxes) in an RTC work item.

Parts Completed:
                  Part 1
                  Part 2
                  Part 3
                  Part 4

In the query of the work items I would like the following output:

ID,      Summary,     Parts Completed,      Waiting on Parts
1        ABC               Part1,                         Parts 3
                                Part2                         Parts 4

Is there a recommended way to get the "not" of the values set on Parts Completed (ie Waiting on Parts)?

I was thinking that I could configure another field Waiting on Parts (which is hidden from the form) and on save update the Waiting on Parts value to the opposite of Parts Completed.

Is this possible?

Is there a better way?

Thanks!