You cannot do what you have outlined here with the current version of the New Relic agent. That's not how the agent works; that's not how New Relic works.
You have a single application whose performance should be considered as a whole. If you were able to route the performance data to different apps, how could you see that a problem in one app is affecting the other app? How can you correlate events and metrics when they are in separate apps?
More specifically, someone could attack app A and negatively impact app B, and that might appear in the performance data for app A, app B, or both. That's why this isn't supported: you don't put up artificial walls in the performance data for a single app running on a single server.
Use the agent the way it was intended, and use the New Relic transactions page in APM and the Web transactions analysis report to filter down to the transactions you care about. You can also use the Insights event explorer to filter and chart your Transaction
data.