Mira este ejemplo que es similar a lo queres:
http://www.victorblasco.es/gm/example6.html
Hace algo así:
Código HTML:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Ejemplo Colocar</title>
<script src= "http://maps.google.com/maps?file=api&v=2&key=ABQIAAAAg_2UIEV5rd9OVgNSGNfsyxTaN__vuAQAUAfJwnfsk7h_mauWkxSYbIJkdkwH1e7uYk7faoLIELG-Tw"
type="text/javascript"></script>
<script type="text/javascript">
function load(lugar) {
if (GBrowserIsCompatible()) {
var map = new GMap2(document.getElementById("map"));
map.setCenter(new GLatLng(0,0), 0);
map.addControl(new GSmallMapControl());
map.addControl(new GScaleControl());
map.addControl(new GMapTypeControl());
GEvent.addListener(map, "click", function(overlay, point){
if(overlay){
if(overlay.title)
map.openInfoWindowHtml(overlay.getPoint(), overlay.title);
}
});
var geocoder = new GClientGeocoder();
geocoder.getLatLng(lugar, function(point) {
if (!point) {
alert("Lugar no encontrado");
} else {
map.setCenter(point, 12); // 12 indica el valor de zoom
var center = new GMarker(map.getCenter());
center.title = lugar;
map.addOverlay(center);
map.openInfoWindowHtml(center.getPoint(), center.title);
}
});
var center = new GMarker(map.getCenter());
center.title = "Centro del mapa";
map.addOverlay(center);
map.openInfoWindowHtml(center.getPoint(), center.title);
}
}
</script>
</head>
<body onUnload="GUnload()">
<input type="text" name="lugar" id="lugar" />
<input type="button" value="Enviar" onclick="load(document.getElementById('lugar').value);" />
<div id="map" style="width: 600px; height: 400px"></div>
</body>
</html> Esto: ABQIAAAAg_2UIEV5rd9OVgNSGNfsyxTaN__vuAQAUAfJwnfsk7 h_mauWkxSYbIJkdkwH1e7uYk7faoLIELG-Tw es la api key