Use Debian lenny package on Debian squeeze

[ML mail <mlnospam@yahoo.com>]

Dear Debian users,

I would like to know if it is possible to use a Debian lenny package on a Debian 
squeeze installation and if yes how (what apt-get commands and/or modifications 
in sources.list)? 


Let me explain why: I am using Bacula to do backups on a Debian lenny box and 
upgraded one server being backed up to Debian squeeze. Since then the backups 
are not running because Debian squeeze uses Bacula version 5.0 and the backup 
server (lenny) uses Bacula version 2.4. It is know that these two versions are 
not compatible together anymore (rejected hello command error).

So I was wondering if it is somehow possible to install the Debian lenny 
versions of bacula-common and bacula-fd packages on Debian squeeze...?

Many thanks in advance for your help.
Regards