[closed] how to add an “onclick” function to a marker?

I have a marker such as this

var feature = new OpenLayers.Feature.Vector(
                      new OpenLayers.Geometry.Point( lng,lat ).transform(epsg4326, projectTo),
                      {description:'something'} ,
                      {externalGraphic: 'somepic.png', graphicHeight:34, graphicWidth: 21, graphicXOffset:0,   
                                      graphicYOffset:0 }); 
vectorLayer.addFeatures(feature);
map.addLayer(vectorLayer);

i was wondering if there is a way to add onclick function to the markers, so an example use would be something like

feature.onClick(function (){
   alert("clicked");
});