[Zope] specify passive ports for ftp

Hi I have a problem using Zope passive ftp. * We have configured our firewall for high security. * The problem is using passive ftp because one can not know wich ports being used for communication. * Opening all high ports on the firewall is not an option. Is it possible to specify which ports Zope er allowed to use for passive ftp (like you edit 'ftpaccess' for other ftp servers), so that we can reconfigure the firewall for these ports? If not, are there any other way of solving this?...except for modify ftp source code. Thanks for all help! Regards Arnt-Hugo Nilsen