Sandbox Node.js child_prosess

I'm creating a manager to run indiviual Node.js apps in a shared enviorment.

I have this master.js:

var spawn = require('child_process').spawn,
  _ = require('underscore');

var env = {
  PORT: 3001
}

_.extend(env, process.env);

var child = spawn('node', [ 'child.js' ], {
  env: env
});

// trying to get something like this to work
child.on('bindtoaport', function (port) {
  if (port !== env.PORT) {
    child.kill();
  }
});

The last statement, obviously, does not exist. I want to intercept the system call (before it reaches the system), see which port it will bind to, and then kill it if it's the wrong port.

Is this possible in vanilla node.js? or does it require some crazy binding to some native OS module?