....ok.
So you want to CHOOSE IF it should or should not be enabled?
So... sometimes it should do a menu, sometimes not?
After a search, here's what I got...
The functions usually available apply to the entire document, not elements. So you can't just specify elements.
Seems like you can use:
<element onmousedown="if(event.button==2){alert('right mouse button clicked!');}">
to decide what to do.
However, that might not work on the background.
but if you just want it on links, then that's possible.
However...
<a href="something.htm" target="_blank">
is the MUCH better solution for this. It forces a new window and will be supported with or without javascript AND doesn't annoy the user like no right click scripts do.