Every n*x milliseconds I perform an action where n = 0, 1, 2, ...; x is some increment.
Example - every 25 milliseconds I perform a calculation.
This action
Here's a high-precision timer I wrote. I get roughly <1ms avg precision on 25ms interval. But if Windows is busy it may come in late. It's fairly lean on CPU utilization. Feel free to use. It uses Sleep(1) when the next tick is more than 15ms away and then SpinUntil (which yields as needed) to keep CPU usage at bay. Uses .NET4 features.
Link: High Precision Timer