[NTG-context] layers for odd and even pages

Dear list, I have the following sample: \setuppapersize[A5] \setuppagenumbering[alternative=doublesided,location=] \definelayer[testodd][state=start] \setlayer[testodd]{Odd page} \definelayer[testeven][state=continue] \setlayer[testeven]{Even page} \setupbackgrounds[page][background={testodd, testeven}] \starttext \dorecurse{5}{\dorecurse{\recurselevel}{\input zapf\par}\page[right]} \stoptext I need different layers in even and odd pages and that they are hidden on empty pages. Which is the way to do it? Many thanks for your help, Pablo -- http://www.ousia.tk