VB.net 2005 (.net 2.0) - Group By DataTable

I need to Filter / Group By a DataTable
I need to be able to do a Select Account Number = 1111 and then Group those results by the Product Code

How can I Filter a DataTable and Group the Results?

This is an example...but it doesn't work...
Dim foundRows() As DataRow = DE_ProductCodes.Select("AccountNum = " & AcctNum.Text & " group by ProductCode")

Thanks,
Mark