Hi, 

when designing some documents, I hope I can set a global layout and 
another layout for the first page of all chapters. I have defined two 
layouts as follows:

\setuppagenumbering
[alternative=doublesided,
 location=]

% global layout for the whole document
\setuplayout
[backspace=2.5cm,
 width=16.5cm,
 topspace=2cm,
 height=25.2cm,
 header=\lineheight,
 headerdistance=\lineheight,
 footer=0cm]

% layout for the first page of Chapters
\definelayout
[firstpage]
[height=26.2cm,
 footerdistance=\lineheight,
 footer=\lineheight]

\starttext
\chapter{First Chapter}
I am in the first page.
\page
I am in the second page.
\stoptext

my question is that how I can apply this `firstpage' layout 
to the first page of the chapter `First Chapter' and switch back to 
the global layout after the first page of this chapter?

Best Regards,Tim