The idea to conditionally formatting cells in an ASP.NET data grid lies simply with the ItemDataBound Event of the datagrid.
Example:
protected void gridData_ItemDataBound(object sender, DataGridItemEventArgs e)
{
if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
{
Customer cust = (Customer)e.Item.DataItem;
Int32 daysRemaining =cust.SubscriptionDaysRemaining;
if (daysRemaining <= 0)
{
e.Item.Cells[12].ForeColor = Color.Red;
e.Item.Cells[12].Font.Bold = true;
e.Item.Cells[12].Font.Italic = true;
e.Item.Cells[12].Font.Size = new FontUnit(16);
}
}