Need help creating word autocorrect

[Kamchatka_]

I'm trying to create a custom autocorrect for word which will convert the text "rms1" to the symbol for root mean squared, (c^2) overbar, I know how to create this symbol in word (alt + q, select the overbar "accent" and type c^2 inside it) and I know how to create custom auto corrects that autocorrect to text. However, I can't work out how to make the aucorrect produce this symbol. 

 

If you know how this could be achieved then I would be very grateful for some help.

 

Thanks

 

P.S.

I write a fair number of equations in word documents so if anyone knows if there is a way to stop word automatically capitalising the first letter on a line if (and only if) it is on its own, then that would also be very helpful