How to change the order status of an order?

Hi,

I am not able to change the status of the order.

Currently, am trying with the following code.

OrderGroup orderGroup = (OrderGroup) purchaseOrder;
orderGroup["order_status_code"]=2;
purchaseOrder=basket.saveOrder();

What is happening? OrderGroup is an abstract class so i cant create the
OrderGroup object. I want to chage the status of the order to say,
"Pending" instead of the default "New Order".

How do i do that?

Many thanks
Disha