[Freeswitch-users] About screen pop with freeswitch？

Hi, I am playing with freeswitch scripting with lua. I want call to number, ex 1000, a script lua will process the call ( as an IVR), then transfer the call to an extension (or transfer the call to a queue, to get a free agent). Questions: How I add a pair data (key/value. ex ID/1234) to the call in the lua script? How can check the data attached is avaliable to the end extension? What you use to make screen pop call data when the call ring in the extension? Thanks