[NTG-context] test for new page

Can someone indicate how one can easily test for a new page in a list environment (or, indeed, anywhere else)? In one implementation of a listing, repeated sequential items or elements of items are suppressed, but I would like to repeat them when they occur at the top of a new page. I imagine that there could be an easy test for a new page or the text line number. Thanks, in advance, for any hints. Alan