TFS Api - trigger test run conditionally (when new files come)

I'm trying to get acquainted with test automation using Microsoft TFS Api.

I've created the program which runs my test set - it uses code similar to one described here, e.g.:

var testRun = _testPoint.Plan.CreateTestRun(false);
testRun.DateStarted = DateTime.Now;
// ...
testRun.Save();

I believe this forces them to start as soon as any of agents can run them, instead of being delayed to certain time. Am I wrong? Anyway, it works all right.

But I was told by my lead that the task should be started each time the new input files are copied to certain folder (on the network I think, or perhaps in TFS).

So I'm searching for a way which allow to trigger tests on some condition - but currently without any luck. Probably I miss proper keywords.

I only found something vaguely related here but it seems they say it is not possible in a proper way.

So are there any facilities in TFS / MTM, any ways or approaches to achieve my goal? Thanks in advance for any hints / links.