Hello Pitsch,
Most probably you are referring to RadChart instead of RadGrid. As for the PointMark I am not exactly sure what the problem is. StyleSeries class has a property named "PointMark" of type StyleMarkerSeriesPoint. I am attaching an screenshot from this property in reflector. Perhaps I am missing something?
Let me know how I can help further.
Greetings,
Vladimir Milev
the Telerik team