Well, we already have e for and cleg for that.
In the case of certain subordinate conjunctions which also function as question words/demonstrative/interrogative adjectives when they are modified by a preposition, the preposition, as always, becomes its suffix. These interrogative pronouns can actually be seen as contractions here, and it may make more sense to extend them to their full meaning to better understand the grammar, using the word “which.” (who = which person, what = which thing, where = in which place, why = for which reason, how = in which manner, how much = which amount, and so on) I will not make a distinction between the interrogative forms and the demostrative forms, simply for lack of imagination.
* By the way, for the sake of giving full credit where it is due, i should include the following conversation that went on as i was typing this section.
mioethdrauci: okay, i need a good word for "but"...got any suggestions?
domotran: in what lang?
mioethdrauci: hmmm, that's not bad. i like that...thanks :O)