global information in Calc plugin

Hello,

I would like to extend the capabilities of my C++ Calc plugin. I open
Calc and made some calculations in my plugin in the first spreadsheet
"A" (e.g. using set() methods for data - I can retrieve the content
using get() method in A). Selecting "file->new spreadsheet" I open a
second spreadsheet "B". I want to share the calculated value in "A" with
"B" (using get() function). Currently the C++ plugin seems to work per
spreadsheet, i.e. I cannot share information of A with B (the get()
function seems to store data per spreadsheet). I have to recalc values
in B althoug they are calculated in A. 

Is it possible to share information between spreadsheet A and B? Which
datastructures do I have to use in the C++ plugin?

Kind regards,
   Lars