Window level setting over accessibility

I am working on a Mac OS X application that controls a window owned by another application. For this I use Accessibility.

I have already managed to move the window and request its properties from my application. Now I need the window to remain "always on top". Based on another post I need to set the window level to NSFloatingWindowLevel. Is this possible by the Accessibility API? I do not see any Accessibility or Carbon that will match the window level.