[NTG-context] Calling \followtokens from with in metapost

Hello list, How can I call the \followtokens macro (or a similar solution) from within metapost? Specifically, I want to integrate text between the semi-circle arcs in a rainbow-like structure (with the text placed inbetween the arcs, that should alsó be drawn). The text should not be stretched but center on the top, flowing evenly distributed on each side. This link will give you an idea: http://www.heilsuefling.is/heilsuefling/upload/images/whp_in_general/determi... How can this achieved? Regards, Magnus