You will need to speak to the appropriate people at your work-place, like the IT Administrator or whoever is in charge of the network and see if they can help you. Ports for DCC can be set in ALT+O > Connect > Options > [Advanced...]. Default ports are 1024-5000. You can set ports higher or lower than that if you wish. You need at least 2 ports for every DCC connection you wish to make.

If you're not allowed to set up DCC at your work then we cannot and will not help you. It would be bad if you ended up infecting your work's network with a virus or trojan, possibly very damaging to the company you work for, and if you evaded their rules in the process, it's quite possible it will cost you your job. Hardly worth it!