How can I limit FPS in windowed mode

[FlimFlamm 509]

There are two methods of limiting FPS that I know of, but both of them only work when in full screen (Vsync and hardware based framerate capping)

Here's my dilemma:

Twitch.tv has a default 16:9 aspect ratio web player (16:9 is the most common aspect ratio). My monitor is 1680 x1050 (16:10 or 8:5 ) and so when I stream people see black bars at the side edges of my stream on unless they also have a 16:10 monitor and are watching in full screen. I overcame this by forcing DayZ into a 16:9 resolution in windowed mode, and just broadcasted that instead of my entire screen and this seems to work fine... However, I'm trying to improve the quality of my stream and the most glaring issue I can identify right now is the fact that my frames currently are out of control and fluctuate wildly (from 60 in cities to 170 when looking at the ground to 1500 in loading screens (good work devs, but seriously, i need to limit these bad boys)).

If anyone knows how i can limit frames in windowed mode I would be forever grateful.

(I have checked but it seems like my GPU does not have dynamic vsync enforcement)

GPU: Radeon HD 7700

CPU: i5-3570k