^^ I had something similar to this but seems to have stopped working in some of the more recent updates. Maybe I just need to spend some time getting it setup again. The script I've got installed is called "powertool" - although i just made my own form and assigned the included commands to my own popup for ease of use.
It's actually very easy to set this up, I still use the po2 grid settings because I am cute like that but you can set it up to what ever metric unit you want: I can change grid settings on the fly without losing my selection: The menus I have as buttons on my main viewport so I can quickly change the settings while I work.…