vB4 how to add bold display into a link ?

[محروم.كوم]

hello,

I want to add the fonction [ b ] (bold) and [ u ] underline when a link is diplaying only into a message like this :

vbulletin original diplay : this is a link


what i want to do : this is a link

Do you know how i can do that ? __DEFINE_LIKE_SHARE__