How do I override notifyUserMessage to have my code there?

Also here is a fragment of my push page:
ls = "";
page.onEngineCreation = function(lsEngine) {
lsEngine.connection.setLSHost("UFD-SQL2008TEST.ufandd.local");
lsEngine.connection.setLSPort(8080);
lsEngine.context.setDebugAlertsOnClientError(debug Alerts);
lsEngine.context.setRemoteAlertsOnClientError(remo teAlerts);

lsEngine.connection.setAdapterName("PROXY_HELLOWOR LD");
lsEngine.changeStatus("STREAMING");
ls = lsEngine;
}
page.bind();
page.createEngine("HelloWorldApp", "LS", "SHARE_SESSION");
var pushtable = new NonVisualTable(["floorupdate"], ["scan"], "MERGE");
page.addTable(pushtable, "hellotable");
pushtable.onItemUpdate =
function(itemPos, updateInfo, itemName)
{
// send completed scan to the front-end
if (updateInfo.getNewValue(itemPos) != "")
{
serverData(updateInfo.getNewValue(itemPos));
}
};
function sendMessage(message)
{
ls.sendMessage(message);
}
After fireing ls.sendMessage(message) LS console shows an error "unknown function" or something.
Am I too far from what I am looking for (sending message back to server)?

Thanks for your patience.