[HELP] proxy setting

Here's my question:

My company use ISA as proxy server and MIS gave me the proxy server address such as ISASRV:8080 and install the Firewall Client in my PC. I can use the IE to browser the FTP site and download the file. The problem is I can not use normal FTP client to connect to FTP site.

There are lots of proxy type setting in FTP client such as FlashGet or FlashFXP, like:

FTP <User user@host:port>
FTP <User user@host port>
FTP <Open host>
FTP <Site host>
FTP <Site user@host port>

I can not get any discription about these proxy setting from FTP client user guide. Anybody can teach me what's difference about these proxy settings and how do I use the proper setting to let me connect the FTP site by FTP client? Thanks for help.

Jacky