[flexcoders] Dynamic data for AdvancedDatagrid in flex 3

[letterpigeon]

I'm looking into using the flex 3 AdvancedDataGrid to display 
hierachical data, an example of such hierarchy is: 


private var dpHierarchy:ArrayCollection = new ArrayCollection([
                          
                                {Status:"valid", "Block 
Level":"B", "Reference Number":"1", children: [
                                        {Status:"valid", "Block 
Level":"A", "Reference Number":"1"}
                                        ]
                                }
                          
                        ]);

.  The problem I'm facing is that I do not know the number and name 
of the columns at coding time (these configuration will be fetched 
from server).  Any suggestion on how to create such data provider?  
I've looked into creating an object as follow:

package com.ms.pbcustody.fileimport.remote.domain
{
        public class FileMetaData
        {
                public var blockLevel:String;
                public var referenceNumber:String;
                [ArrayElementType="FileMetaData"]
                public var children:Array = new Array;
        }
}

but even then, I still need to know the columns at coding time.  Any 
suggestion or example code would be greatly appreicated.  Thanks.

Regards,
Ban