using streamstats and stats together

i'd like to produce a field per event that's the running sum of some field as a percentage of the total sum of that field over the whole search.

for example, if this were excel, my sheet would look something like this:

+-----------------------+---------------+-------------+
| original field values | running total | what i want |
+-----------------------+---------------+-------------+
|                     1 |             1 |         20% |
|                     1 |             2 |         40% |
|                     1 |             3 |         60% |
|                     1 |             4 |         80% |
|                     1 |             5 |        100% |
+-----------------------+---------------+-------------+

i see that streamstats or accum can generate my "running total" column, but to get my "what i want" column, i need the output of stats c() or stats sum(), which destroys the individual events.

i feel like it might be a job for a sub-search and appendcols, but i haven't been able to work it out.

thanks in advance, orion