Using EXSLT functions from Microsoft InfoPath

Hi,

I tried to substract two dates in InfoPath using XSLT.
It seems that the built-in XSLT functions does not support this.
I found EXSLT: it seems great.
But I can not get it work in InfoPath.
Could anyone help me (even with some code example) how to import 
EXSLT functions to use them in InfoPath.
Or please tell me if I am on a wrong way and offer me how to solve my 
problem (substracting dates in InfoPath)

Thanks in advance,
Márton Rideg



________________________________________________________________________
Halld és lásd a 20. századot! Cikkek és videók a század történelmi eseményeiről
az [origo] Múltkor oldalán. http://mult-kor.hu/cikk.php?article=12020