Sorry for the delayed reply.
Javascript code:
/*
    Usage:
    
    var a = FindInPsm('test');
    for (var i in a)
        Debug.Trace(a[i].Email);
*/
 
function FindInPsm(sTextToFind) {
    var oContainer = [];
    for (var oContact = new Enumerator(Messenger.MyContacts); !oContact.atEnd(); oContact.moveNext()) 
        if (oContact.item().PersonalMessage.indexOf(sTextToFind) !== -1)
            oContainer.push(oContact.item());
            
    return oContainer;
}