Custom Data Label and Formatting in Chart

Hi,

I'm a novice in vba. I know there is an addIn which makes exactly what i want. but since i'm at work and i can't use addins i'm asking for a little vba code.
I have a xyscatter chart where I want to label and format the data point depending on a value that is in a range of cell (B2:B33). If the value in this range is "C", the data point should be labeled with "C" and the point should be a red square. Every other point should stay as it is.

Thanks for your help,
alexandre