You need to figure out the ID of html table which contains your related list. You could use a Firefox plugin for that (I prefer Firebug, but Web Developer Toolbar is also cool). For Internet Explorer... I guess the "debugger;" statement put somewhere in JavaScript would work if you have Visual Studio or some IE plugin installed.
Whatever the means, you should be able to pinpoint to HTML similar to this:
<div class="pbBody" id="0017000000Lg8Wg_RelatedOpportunityList_body">
<table class="list" border="0" cellpadding="0" cellspacing="0">
...
Now have a look at JavaScript in my answer, especially this part:
var htmlTable = document.getElementById('j_id0:j_id2:j_id7:accountTable').getElementsByTagName("tbody")[0].getElementsByTagName("tr");
for (var i = 0; i < htmlTable.length; ++i) {
names.push(htmlTable[i].getElementsByTagName("td")[0]);
// We need to sanitize addresses a bit (remove newlines and extra spaces).
var address = htmlTable[i].getElementsByTagName("td")[1].innerHTML;
addresses.push(address.replace(/\n/g, "").replace(/^\s+/,"").replace(/\s+$/,""));
}
Insert the ID you have found into first line. Figure out which <td> cell contains your latitude and longitude information. You can again find it out with your debugger or experiment by putting alert() box inside the loop.
Last part is that you don't need to geocode your addresses, you already have LAT and LONG. So skip directly to function finalizeDrawingMap() and reuse it's content. You can skip the part that tries to guess best zoom (or even better - check Google Maps API if there's better trick for it; that was quick and ugly hack). The core of what you need lies in
for(i=0;i < coordinates.length; i++){
markers.push(new google.maps.Marker({ position: coordinates[i], map: map, title: names[i].getElementsByTagName("a")[0].innerHTML, zIndex:i}));
...
}
Good luck & welcome to StackOverflow :)