patched bad conditional compilation condition to
#if NumberByKey("IGORVERS", IgorInfo(0)) < 6.1
DoUpdate // general update (prior to IP6.1)
#else
DoUpdate /W=$DBwin // update this graph only (/W flag is new in IP6.1)
#endif

The first fully functional release.

The coordinate system issue has been resolved, now both "relative" and "absolute" coordinates are ok.

Not tested on Mac, but I'm waiting to hear complaints...

This is the first release. A minor issue about coordinate systems persists, so the version number is 0.99a.
Tested on IP6.03(Win). May not work on Macs due to the outstanding minor issue.

Minor issue: Problem translating mouse coordinates (pixels) to window coordinates (points).
Current workaround: hard-wired the dartboard to be centered in its window.
Description: The code of the hook function works for dartboards drawn with both relative and absolute coordinates. But when the window is resized, the code breaks for "absolute dartboards". This also happens when the origin of the dartboard is off-center. I fear this means that the code will also not work on Macs.

This is well-tested working code. Since there is still one minor issue, the version number is only 0.99. I'm afraid that this version needs IP6.10 beta 5, but this may change in the near future.

The minor issue is:

When the dartboard is drawn in absolute coordinates, the window must not be resized. Otherwise, the click location code in the hook function breaks. The "Pixels" (mouse coordinates) vs "Points" (window coordinates) problem is actually also the reason why I think this will not work on a Mac. Maybe there is a simple solution (help appreciated), but I could not find a PixelToPoint function in Igor...