Gridview with LinkButton...get Datakey

I have a gridview control that has a Linkbutton, each time the LinkButton is clicked I need a Page Label to update with the new DataKey. 
How do I dynamically change the Label to reflect the Selected Row in the Gridview?
Note, the LinkButton is inside the Gridview and the Label is out side of the Gridview - the Label is a regular page control, the Label should changed each time the use click's the Linkbutton in the Gridview.
Please  help -- thanks,
...