[Jacqueline]

Duplicating the above won't work. You can look at the usertools.php file in the admincp to see how vbulletin deletes sent pms or all pms, which may help you get started.

It looks like a similar query will work, but all three are linked together.

pm
pmid, pmtextid, userid, folderid, messageread, importpmid

pmtext
pmtextid, fromuserid, fromusername, title, message, touserarray, iconid, dateline, showsignature, allowsmilie, importpmid

pmreceipt
pmid, userid, touserid, tousername, title, sendtime, readtime, denied

Your query would need get the $pmtextid based on the fromuserid and dateline in pmtext, and get the $pmid based on the pmtextid in pm, then delete these three rows
delete from pmtext where pmtextid = $pmtextid
delete from pm where pmid = $pmid
delete from pmreceipt where pmid = $pmid

I believe that's what is needed. I hope that helps some!