VK.Widgets.CommunityMessages expand event

var communityWidget = VK.Widgets.CommunityMessages("vk_community_messages", '#YOUR_COMMUNITY_ID#');
setTimeout(function(){
    var widgetID = document.getElementById('vk_community_messages').getElementsByTagName('iframe')[0].getAttribute('id').replace('vkwidget', '');
    var _community_xdm= VK.Widgets.RPC[widgetID];
    _community_xdm.methods._origin_expand = _community_xdm.methods.expand;
    _community_xdm.methods.expand = function( opts ){
        /** your code here */
        _community_xdm.methods._origin_expand (opts);
    }
}, 200);