Automatical enable/disable plugin button on selection change

Hi,

I am looking for a way to enable/disable my plugin toolbar button automatically when the selction changes in the editor.
I've seen that there is an OnSelectionChange event being fire but I don't know how to tell my toolbar button to change it's state. I've managed a state change in the GetState function of my toolbar command but this is only executed when the window loads. How can I force the toolbar button to redraw with the OnSelectionChange event?

Thanks for any help,


Helmut