Chart XML - Changing the ToolTip in a Series

I tried to use the notation that visual studio 2010 gives for charts which is to put a ToolTip="ABC" in the series, but it doesn't seem to override the ToolTip. I also tried ToolTipLabel="ABC" which didn't work. Has anyone done this?

Also, how do you put the value in the tooltip as well? According to VS2010 you would put in something like: ToolTip="My Value: #VAL"

Thanks!