How to get a pointer to MScreensaverPluginHost from a MScreensaverPlugin class?

I am developing a screensaver. I have set the capability EScpCapsPreviewNotification, so when I click "preview" the PluginFunction method gets called. The InitializeL(MScreensaverPluginHost* aHost) method don't get called, so I want to call it from the PluginFunction method. How do I do that?

The PluginFunction method looks like this:
TInt CScreensaverPlugin::PluginFunction(TScPluginCaps aFunction, TAny* aParam) { }
I need to have a pointer to MScreensaverPluginHost to call the InitializeL method. How do I get that pointer?