Mx AdvancedDataGrid - remove divider inside header for text and sort icon

Hi

I want to remove sorting for advanced data grid so i put
sortableColumns="false" and sorting is removed. But you must have notice in
Flex 4.1 and later, there is a vertical separator between header text and
sort icon.So now sort icon is removed but vertical divider is still there.
How to get rid of vertical divider. I am using Flex 4.1 and mx
advanceddatagrid.
DataGrid_VerticaDividerl_Header.png
<http://apache-flex-users.2333346.n4.nabble.com/file/n8073/DataGrid_VerticaDividerl_Header.png>
Added file as screen shot.

Any pointer is valuable.

Cheers
ilikeflex