Identifying Ext Js Button in Selenium !

Hi,

I am not able to identify clickable button in data grid while executing Selenium test.

 Following is the code snippet used to generate button:

var addButton = new Ext.Toolbar.Button(
                              { action: '', disabled: false, handler: onAction, icon: '',
                                iconCls: 'menu-add', params: {},
                                id: 'menu-add' , text: '' });

However, while writing test script, not able to identify this button in data grid.
Have tried following command:

selenium.click("Ext.getCmp('Add')"); &
selenium.click("//input[@name='addButton']");

but of no use.

Please help me out if anyone has some clue.

Thanks,
Prashant