Port forwarding / Behind a unknown firewall

[Pyrasol]

Hi,

I'm a newbie in this forum and I'm not very familiar with FTP stuff.

I've a connection problem: I'm behind a unknown firewall in our company. I can't connect to FTP servers with ports other than 21.
At home, a connection to these FTP servers is ok.
My IP address outside the firewall is a fixed address for all users in our network.
OS: Win2000
FlasFXP: 2.0 / 902

I read something about 'port forwarding', but I've no idea how I've to manage this. I did a search here for this topic, but it's still foggy for me.