how to sort pages starting printing from last page?!

Hi! 
I discovered how to access the Cups API. My problem is that every job i want to 
print contains more then one page, should be sorted by starting printing from 
the last page to the first page.

I watched at the Programmers manual and i didn't find any function doing that 
forme. (or i didn't look more close inside the manual). Can somebody tell me 
how to do that? 

For every help, thank you

Tamer Higazi