Needs assistance regarding the VISA to HK

I am working in India for the company Sonicwall Info Security (sonicwall.com) as th Product support Engineer. I have scheduled my Cisco CCIE LAB exam (cicso.com) on 31st JAN 2012 in Cisco Hong LAB testing center. I have a letter from Cisco requesting to HK Immigration for the entry visa, I need visa for max of 3 days to HK. How do I get this done?

Regards,
Rewanta SUbba