Extract the layer 3 flow between two VM in NSX rest Api

Hi All I ask a question on how to extract the layer 3 flow between two VM

I'm uses this api to extract data from datacenter, "/api/2.1/app/flow/flowstats?contextId=datacenter-21&flowType=LAYER3&startTime=0&endTime=1320917094000&startIndex=0&pageSize=2"

But can how integrate   vm ?

For example i would undestand how integrate tow VM in this api.

Thanks so much