Open infoWindow of specific marker from outside Google Maps (V3)

You are on the right track. You just need to create a separate global array for your Marker objects and push all created markers to this array. When you write out all your company data to html include a call with the index of the marker executed on click. Below is an example code. I used JSON as my data structure to hold company info instead of XML.

<html> 
<head> 
    <meta name="viewport" content="initial-scale=1.0, user-scalable=yes" /> 
    <meta http-equiv="content-type" content="text/html; charset=UTF-8"/> 
    <title>Google Maps Scroll to Marker</title> 

    <script type="text/javascript" src="http://maps.google.com/maps/api/js?sensor=false"></script> 

</head> 
<body onload="initialize()"> 

    <div id="map_canvas" style="width: 900px;height: 600px;"></div> 
    <div id="companies"></div>
    <script type="text/javascript"> 
        var map;
        //JSON of company data - equivalent of your XML 
        companies = {
            "data": [
            {
                "name": "Company 1",
                "lat": 42.166,
                "lng": -87.848 
            }, 
            {
                "name": "Company 2",
                "lat": 41.8358,
                "lng": -87.7128 
            },
            {
                "name": "Company 3",
                "lat": 41.463, 

                "lng": -88.870 
            },
            {"name":"Company 4",
            "lat":41.809, "lng":-87.790}		
            ]
        }
        //we will use this to store google map Marker objects 
        var markers=new Array();
        function initialize() {
            var chicago = new google.maps.LatLng(41.875696,-87.624207);
            var myOptions = {
                zoom: 9,
                center: chicago,
                mapTypeId: google.maps.MapTypeId.ROADMAP
            }
            map = new google.maps.Map(document.getElementById("map_canvas"),
                myOptions);
            listCompanies();
        }		 

        function listCompanies() {
            html = ""
        //loop through all companies
        for (i=0;i<companies.data.length;i++) {
        //get the maker postion
        lat  = companies.data[i].lat
        lng =  companies.data[i].lng

        //add google maps marker
        marker = new google.maps.Marker({
            map:map,
            position: new google.maps.LatLng(lat,lng),
            title: companies.data[i].name
        })
        markers.push(marker);
        html += "<div onclick=scrollToMarker(" + i + ")>"+companies.data[i].name+"</div>";
        }
        //display company data in html
        document.getElementById("companies").innerHTML =html;
        }

        function scrollToMarker(index) {
            map.panTo(markers[index].getPosition());
        }
</script>

</body> 
</html> 

Ok I added another solution for you - uising your code. This one uses your bindInfWindow function to bind the DOM (HTML) click event to open info window and scroll to marker. Please note that because you are loading companies dynamically the divs (or some other tags) that hold their names and ids must exist in the DOM BEFORE you start binding events to it - so the first function you need to execute is the one that renders companies HTML (not the map init). Please note I have not tested this one as I do not have your data..

//you must write out company divs first

<body onload="showCompanies()">



<script>
//JavaScript Document
var map;
//this is your text data
var markers = new Array();


//you need to create your company list first as we will be binding dom events to it so it must exist before marekrs are initialized
function showCompanies() {
 downloadUrl("/ajax/member-xml-output.php?country=BE", function(data) {
    var xml = data.responseXML;
    markers = xml.documentElement.getElementsByTagName("marker");

    for (var i = 0; i < markers.length; i++) {
      var company = markers[i].getAttribute("company");

      markerId = "id_"+i;

      company_list += "<div id="+markerId+">"+company+"</div>";
    }       

    //display company data in html
    document.getElementById("company_list").innerHTML = company_list;

    //now you are ready to initialize map
    initialize_member_map("lang")
  });
}

function initialize_member_map(lang) {
  map = new google.maps.Map(document.getElementById("large-map-canvas"), {
    center: new google.maps.LatLng(50.85034, 4.35171),
    zoom: 13,
    mapTypeId: 'roadmap'
  });




    var xml = data.responseXML;

    var bounds = new google.maps.LatLngBounds();
    //your company data was read in and is ready to be mapped
    for (var i = 0; i < markers.length; i++) {
      var infoWindow = new google.maps.InfoWindow;
      var company = markers[i].getAttribute("company");
      var address = markers[i].getAttribute("address");
      var type = markers[i].getAttribute("type");
      var uid = markers[i].getAttribute("uid");
      var point = new google.maps.LatLng(
          parseFloat(markers[i].getAttribute("lat")),
          parseFloat(markers[i].getAttribute("lng")));
      var html = "<b>" + company + "</b> <br/>" + address;
      bounds.extend(point); 
      var marker = new google.maps.Marker({
        map: map,
        position: point,
        uid: uid
      });
      //add the new marker object to the gMarkers array

      markerId = "id_"+i;
      bindInfoWindow(marker, map, infoWindow, html,markerId); 

    }       
    map.setCenter(bounds.getCenter());
    map.fitBounds(bounds); 


}

function scrollToMarker(index) {
    map.panTo(markers[index].getPosition());
}

function bindInfoWindow(marker, map, infoWindow, html, markerId) {
  google.maps.event.addListener(marker, 'click', function() {
    infoWindow.setContent(html);
    infoWindow.open(map, marker);
  });
  //bind onlcick events to the div or other object in html
  markerObj =  document.getElementById(markerId);
  //you can create DOM event listeners for the map
  google.maps.event.addDomListener(markerObj, 'click', function() {
    infoWindow.setContent(html);
    infoWindow.open(map, marker);
    map.panTo(marker.getPosition());
  });

}

function downloadUrl(url, callback) {
  var request = window.ActiveXObject ?
      new ActiveXObject('Microsoft.XMLHTTP') :
      new XMLHttpRequest;

  request.onreadystatechange = function() {
    if (request.readyState == 4) {
      request.onreadystatechange = doNothing;
      callback(request, request.status);
    }
  };

  request.open('GET', url, true);
  request.send(null);
}
function doNothing(){
}

</script>