asp.net dynamic data web site : passing default value while inserting/updating records

I am working in ASP.NET Dynamic Data web application and have an issue of passing default value while inserting/updating records. In my application all table has following common column:

• CreatedBy (Default Value : Logged in user)
• CreatedDate (Default Value : DateTime.Now)
• modifiedBy (Default Value : Logged in user)
• ModifiedDate (Default Value : DateTime.Now)

I want to keep these column hide in Insert and Edit page and want that default value will be inserted automatically in the respective column.

Please suggest me.

Thanks paul

solution i have implemented finally:

protected void FormView1_ItemInserting(object sender, FormViewInsertEventArgs e)
   {
      e.Values.Add("CreatedBy", HttpContext.Current.User.Identity.Name);
      e.Values.Add("CreatedDate", DateTime.Now);
    }

 protected void FormView1_ItemUpdating(object sender, FormViewUpdateEventArgs e)
    {
      e.OldValues.Add("ModifiedBy", null);
      e.OldValues.Add("ModifiedDate", null);
      e.NewValues.Add("ModifiedBy", HttpContext.Current.User.Identity.Name);
      e.NewValues.Add("ModifiedDate", DateTime.Now);
   }