VLC application is a big issue in site because of installed on almost of the client without any requirement.

I want to block the access of the vlc. How to complete the task?

How to block the access of Application using Symantec Endpoint Protection's Application and Device Control (ADC) policies

http://www.symantec.com/business/support/index?page=content&id=TECH185907

See this thread

https://www-secure.symantec.com/connect/forums/how-can-i-block-media-files-my-network-symantec

SEPm knowledgebase here

http://www.symantec.com/business/support/index?page=productlanding&key=54619

Check the thread

https://www-secure.symantec.com/connect/forums/how-block-vlc-and-media-players-sepm

How to block the access of Application using Symantec Endpoint Protection's Application and Device Control (ADC) policies

edit

How to use Symantec Endpoint Protection to block or log legitimate but unauthorized software usage

You can use ADC, find all the info about it in the SEP knowledgebase

http://www.symantec.com/business/support/index?page=productlanding&key=54619

In the firewall policy you can create a rule to block VLC executable file. Let me know if you need any help to create this rule.