Webdatagrid column summary by group

Hello,

I am using a webdatagrid (infragistics) in my ASP.NET application.

My columns are ID, Name, Duration.

each ID has multiple records so it is not a primary key.

I want the grid to show summary by ID for example if i have

ID:1 Name:blah Duration:1

ID:2 Name:blah Duration:3

the grid needs to show the summary 4 (3+1) for ID 1 on so on...