This is not a trivial task, but it can be achieved by modifying the HeaderCellStyle of a column. When you redefine the ControlTemplate of the HeaderCell, you can insert custom UI elements and arrange them.
I have attached a small sample project that does something similar to your scenario. You can use it as a starting point and adjust the layout of your a, a1....c2, c3 labels in a manner that you like. You should be looking for the Grid that is immediately inside the <ControlTemplate TargetType="GridView:GridViewHeaderCell"> tag.
One important thing to note is that when you customize the default header cell template you will lose a lot of built in features such a resizing, filtering, etc.
Please, examine the sample project and let me know whether it will work as a starting point for your custom layout.
Is solution for this problem that maintains the functionality of the column?
what about the telerik team , is this feature will be available in the next release?
answered on 25 Aug 2009, 01:36 PM
Hello Yossie C,
Here you may also find a solution that preserves the features of the column headers.
We are working towards adding this as an internal feature of RadGridView but I can not promise it for the very next release.