Writing a plugin to add text

Hi there,

I'm writing a plugin that shows a dialogue with a list selected from a database and when the user chooses an item, that item is added to the editor.
I'm completely new to writing plugins for ckeditor. I've read some documentation and I'm now so far I can add text to the editor

(function()
{
   var a =
   {
      exec:function(editor)
      {
        editor.insertHtml('Hai!');
      }
   };
   
   CKEDITOR.plugins.add('addfromlist',
   {
      init:function(editor)
      {
         editor.addCommand('addfromlist', a);
         editor.ui.addButton('addfromlist',
         {
            label:'Add some text from a list',
            icon: this.path + 'addfromlist.png',
            command: 'addfromlist'
         });
      }
   });
})();