The code is simple and would look like this:
ULONGLONG Ticks = 0;
Ticks = GetTickCount64();
// some code to time
Ticks = GetTickCount64() - Ticks;
Note: GetTickCount64 returns the number of ms since the system was last booted. Theoretically you might have check for wrapping of the clock; however, 2^64 ms or ~49.7 days is a long time. If you are worried about that, you might consider other APIs that keep track of the full time with a ms resolution.