Flex add a tree in datagrid in column header

I have a question regarding the flex datagrid. I'm just wondering 开发者_运维知识库if it's possible to put a horizontal tree view in column header. Each node will become a column in datagrid. I saw there are similar examples for each column. But what about the column header? Something like below:

           node1                node2
             |  child1  child2    |   child1 child2
             |——–-|------|--------|----|------|

—————————————————————————————————————————————— +node1

 |—child1

 |—child2

+node2

 |—child1

 |—child2