Jmeter - wait for a specific response

our application is testing file upload and I'm curious if I can make Jmeter wait for a specific response and then report collective time.

What I have now is:

whileLoop()
  -- HTTP Sampler
  -- JSON Extractor

JSON Extracor pulls out a specific field and if it's not null then the loop stops.

The problem is that JMeter doesn't report response time as a sum of all the responses (response times) it had to make and that is what I'm looking for. Is there a way to implement this?