[NTG-context] how to implement buttons, navigator in context's presentation

hi, all in Hans Hagen's "Metafun context mkivhttp://www.pragma-ade.com/general/manuals/metafun-s.pdf" page 208, there is some buttons example, I want to know how to implement a complete buttons in context, Thanks in advance! another, in Presentations (screen documents) <http://Presentations (screen documents)>, there is three examples, but they are not able to be compiled by the latest context version 2012.12.28 20:30, I hope to get some advanced examples Thanks! BEST REGARDS PengCZ