The following function is called in the zimlet init function, but when create a new mail or open a mail, the new button doesn't show up. No exception reported from the browser, any help is greatly appreciated.

com_zimbra_scs.prototype._addButtons =
function()
{
// Add the Salesforce Button to the Compose Page
this._composerCtrl = AjxDispatcher.run("GetComposeController");
this._composerCtrl._scs = this;
if(!this._composerCtrl._toolbar)
{
this._composerCtrl._initializeToolBar();
}


this._toolbar = this._composerCtrl._toolbar;

// Add button to toolbar
ZmMsg.scsAdd = "Call";
ZmMsg.scsTooltip = "Call the sender.";
var op = {text: "scsAdd", tooltip: "scsTooltip", image: ""};
var opDesc = ZmOperation.defineOperation(null, op);
ZmOperation.addOperation(this._toolbar, opDesc.id, this._toolbar._buttons, 1);
this._toolbar.addSelectionListener(opDesc.id, new AjxListener(this._composerCtrl, this._CallSender));
}

com_zimbra_scs.prototype._CallSender= function(ev) {
var msg = this._composeView.getMsg();
this.msgDropped(msg);
};