Elasticsearch - bucket aggregation selection

Is it possible to perform child or pipeline agg on select buckets?

I have car sales records ("datesold" & "amountsold") and I create a monthly agg histogram. This gives me monthly buckets.

"aggs": { "sales_per_month": { "date_histogram": { "field": "datesold", "interval": "month" } } }

I want 2 sets of outputs (pipeline aggregation), average of "amountsold" for buckets until last month and another output for average of current month's bucket (last bucket). Is this possible?