Categorise and show/hide column headers in datagrid

[aquagal]

Hi,

I am trying to build the following functionality in the datagrid.I need
some help regarding that.

I have a lot of columns in the datagrid.I want to group them into
categories so that when a user clicks a category the category should
expand into its underlying set of columns belonging to that category.So
initially when the grid loads the user only sees the main categories of
the data as column headers.He can click the column headers and they
should expand to display the set of columns and their data for those
columns.

Thanks in advance for your help.