Use a timer. There are 3 basic kinds, each suited for different purposes.
Use only in a Windows Form application. This timer is processed as part of the message loop, so the the timer can be frozen under high load.
When you need synchronicity, use this one. This means that the tick event will be run on the thread that started the timer, allowing you to perform GUI operations without much hassle.
This is the most high-powered timer, which fires ticks on a background thread. This lets you perform operations in the background without freezing the GUI or the main thread.
For most cases, I recommend System.Timers.Timer.