How to complete a link

[lasto]

I have a link that each member has to go to a profile page about them.Not profile page which is built into vbull but something different.

All users names are stored on one page and u select your name from the list.
What i want is to add a link in postbit so upon clicking the link it will take u to the users profile.

Now here is where im stuck

The username of the person who post/thread it is is added to the link

so for example :

profile.php?a=lasto

now the link is easy but the profile.php?a=(username) = must only equal the persons name in the postbit.

How do i add there username to the end of profile.php?a=