LulaViolet on "m^2 translated as « square meter » in function"

I got a little challenge here. I'm working on a website for a client, who has no idea about html/php. In some posts of the website will be some data with square meters. Because the client will fill up the posts, its a bit tricky to make wordpress show square meters as square meters and not as for ex. m^2 without using code (m<sup>2</sup>).
I tried several plugins like wp-Typography and also wp-LaTeX, but the first plugin doens't work and the second one works but not in the way I would like to.
Because I'm better in reading php than actually writing it by my self, I was wondering, if it would be possible to create a function in the function.php who automaticly changes the « m^2 » into the visual of m<sup>2</sup>.
Any ideas? Would be very helpfull.