Well, you've got to learn the language before you can hack it. The computer system isn't an AI. It can't tell if you have created a new word that makes sense.
Esperanto isn't 100% logical, it is not Lojban. So "en" can refer not only to spatial concepts (en la domo), but also to temporal ones (en la jaro 2002), and to abstract concepts (en tiu situacio, en Esperanto, en amo).
"Per" works but means something different, more like "by means of".