how do I get the userid from the lastpost id?

[l3it3r]

On forumdisplay, the lastposter is a 'query' to member.php
is there anyway to get the userid to show up in that link instead?

I ask because I am integrating Zoints Local and the link needs to be structured as such: "z/index.php?id=$blahblah[userid]"

however, right now it's pointing to member.php and not using a standard userid number, it's the one that corresponds to the current thread... anyway to do this?