This study seeks to go beyond a conception of “multilingualism” overtly attached to a view of language as a closed set of rules over-determining the form of utterances purely defined in terms of grammar. This study focuses on a diversity of linguistic practices locally elaborated by the participants in the course of their actions – what has been called a “languaging” activity. This invites us to think about language-at-work and the online development of syntactic and pragmatic resources. Adopting the framework of Conversation Analysis inspired by ethnomethodology, on the basis of the analysis of ten extracts of professional exchanges in multilingual settings, this paper attempts to contribute to the development of a step-by-step examination of the way in which participants process the heterogeneity of their available resources, particularly visible in situations of multilingual interaction.