Something (slightly ) less half-@§§ed than usual.
It seemingly works and I find it handy, mainly because I use (and like) RPN calculators. 
TI fans won't like it, HP ones might.
Not fully-fully tested, as always ideas, suggestions, bug reports are welcome.
 only as (pointless) anecdata, a few years ago I realized that my beloved HP-28C I was using was older than the civil engineer I was working with at the time (and BTW I was still waaay faster with it than him with a "normal" calculator )