How to block all except Yahoo Messenger?

[chickoy3]

i am a pfSense newbie. need help.

i want to block all internet traffic for a specific workstation, 172.23.254.121, except for it's yahoo messenger application which uses tcp port 5050 for messaging.

i tried this configuration:

it didnt work with just lines "NMS_YM1" and "NMS-block" present. i tried adding the "NMS_YM7" line but still not working. the only thing that's working is the workstation is not able to browse the internet.

thanks so much, in advance.