In table add column Insertdate datetime.
This will contain when data is inserted.
In page take hidden field. Store datetime value while calling handler for first button.
Now while calling handler when you want latest data send querystring Lastdate & its value should be hidden field value.
in handler change this
if(context.Request.QueryString["Lastdate"] != null)
{
DataTable dt = GetData(RoleID,CompanyID);
}
else
{
string Lastdate= context.Request.QueryString["Lastdate"]Tostring();
DataTable dt= GetData(RoleID,CompanyID,Convert.ToDateTime(Lastdate));
}
Create method to get latest record.
public void GetData(string RoleID,string CompanyID, DateTime Lastdate)
{
}