Cluster on Marker Layer

[Tessimisst]

Hi everybody,

my task is to create a cluster on a marker layer.

Can anybody tell me how to do that?

Many thanks

My Code:

var antraege=new OpenLayers.Layer.PopupMarker('Anträge', {
        createIconFromData: function (data) {
            return new OpenLayers.Icon (data.icon, {w:25,h:30});
        },
       createHtmlFromData: function (data) {
            return '<p><table style="width: 100%"><tr><td><strong>Antragsnummer</strong></td><td>' + this.html(data.antragsnummer) + '</td></tr>' +
      //'<tr><td><strong>Status</strong></td><td>' + this.html(data.stat) + '</td></tr>' +
      '<tr><td><strong>Fortführungsriss</strong></td><td>' + this.html(data.fr) + '</td></tr>' +
      '<tr><td><strong>Bearbeiter</strong></td><td>' + this.html(data.Bearbeiter) + '</td></tr>' +
      '<tr><td><strong>Auftragsart</strong></td><td>' + this.html(data.Auftragsart) + '</td></tr></table>';
        },
        location: "korrd3.txt"


    });
  map.addLayer(antraege);