Responding to a callback from a child message in node.js

I've run into a problem with node.js and can't figure out the correct way to handle this situation.

I have worker process that handles all the data for a leaderboard. When a request comes in for the leaderboard, I send the request to the worker to handle. The worker will send back the response via the child_process messaging.

My problem is how to efficiently get the response to the callback. This is my first attempt, but wont work as I'm always rebinding the 'message' event to a different callback.

Manager.setup_worker = function () {
  Manager.worker = require('child_process').fork("./workers/leaderboard");
}

Manager.process_request = function (request, callback) {
  Manager.worker.on("message", function (response) {
    callback(response);
  })
  Manager.worker.send(request);
}