clear or remove rows

Hi,
I used the method OwnerDrawCell to draw a text with different color, thanks to Deepankar, but now I have a new problem.
How can I erase the cell contents, because I have the overlay text if you invoke the command twice.
I hope you understand me.
At the moment I use .Clear(C1.Win.C1FlexGrid.ClearFlags.All)

Thanks in advance.
Massimo