Tracking time spent on pair-programmed work items

Hi,

Here's my proposed user story:

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As a pair programmer who is pairing with the owner of a work item, I
would like to track my time spent against the work item, to ensure my
progress and load bars accurately reflect what I have done and have to do.
---

Since work items have a single owner, there seems to be an assumption
that the owner is the only person who is going to spend time on that
item. If two people (the owner and another) pair-program to complete a
work item, there is no way to mark the time spent individually, within
that work item. The 'Estimate' and 'Time Spent' are scoped to the work
item and hence are used in the load and progress bars for the owner of
the work item.

A work around is to create a child task to cover the time spent by the
other programmer in the pair, but this means extra tasks need to be
opened and is less usable than it could be.

Thanks,
Jeremy