Determining if a Window Has a Taskbar Button

I am looking for a way to check if a given window has a taskbar button. That is, given a handle to a window, I need a TRUE if the window is in the taskbar, and FALSE otherwise.

Conversely, I am wondering if there is a way to get a handle to the window that belongs to a given taskbar button, which I suppose would require a way to enumerate through the taskbar buttons.

(The first former is the part that I need, and the latter part is optional.)

Thanks a lot.