jsui detect right mouse click on Win

According to the documentation, the onclick() ( or ondrag() ) function modifier modifier2 should output the state of the right mouse button in Windows.

" function on (x, y, button, modifier1, shift, capslock, option, modifier2)
{
// do something
}
The modifier1 argument is the command key state on Macintosh, and the control key state on PC, and the modifier2 argument is the control key state on Macintosh, and the right button state on PC. Modifier state is 1 if down/held, or 0 if not. "

But in my case the state of modifier2 is always zero. Would anybody know how to interrogate the right button state on PC?