Show data for last 90 days

 I am using an infragistics grid in a user control that currently shows our network status in descending order for the past several months. I would like to show the status for the last 90 days only. Please help and many thanks! My .cs code is shown below:
public partial class UserControls_Network_StatusLog : Port.Base.PortUserControl
{
              protected void Page_Load(object sender, EventArgs e)
             {
              }
              protected void ObjectDataSource1_Selecting(object sender, ObjectDataSourceSelectingEventArgs e)
             {
         ...