The link would be:
HTML Code:
search.php?do=finduser&u=79989&starteronly=1
As compared to the link for find all posts:
HTML Code:
search.php?do=finduser&u=79989
So, modify the template by copying the Find all Posts link and modify as shown above.
The actual code in memberinfo_block_statistics is:
HTML Code:
search.php?$session[sessionurl]do=finduser&u=$userinfo[userid]
But if you are doing this on the showthread.php page, you would use $post instead of $userinfo.
(Also, if you do a search, you may find a mod to do this.)