A program to toggle between prefixes

[salvomic]

hi everybody,

I need an easy way to toggle between prefixes (a,f,p,n,µ,m ... k,M,G,T,P,E) and write them after a number.
For example:
I have 0.135 and I would like to toggle: 135 m, 135000 µ, 135000000 n ...
or I have 135000 and I would like to toggle 135 k, 0.135 M, 0.000135 G and so on...
This purpose having or not having regard to the unit of measure (i.e. V, F, ohm...), like in some Casio calculator (with the ←ENG and ENG→ buttons)...
I mean to toggle back and forward from any number in a simple way (like with user keystrokes or other way with *very few* keystroke pressing)...

Any idea?

Salvo