Quantity confirmed against an order but not able to dispatch

Hi,

I created a material X ,stock entry was made for 3 Qty.Now unrestricted stock is 3

Later on i created a sales order with Material X,2 qty,in the schedule line order got confirmed.Sales order no 1

Next i created a sales order no 2,with material X,2 qty .As 2 materials got already confirmed to sales order 1,Now in schedule line only 1 qty got confirmed.

I created delivery referring sales order 2.System copied only Qty 1 in the delivery screen.I manually changed it  to 2 and issued 2 qty.

Latter on i created delivery with sales order 2,system showed a log that only 1 qty is available.

Note:In the delivery item category,the check over delivery status is B-Situation rejected with an error message.

My question:How delivery for order 2 can be done with 2 qty.As system have confirmed for 1 qty.

Means check over delivery status is B-Situation rejected with an error message will do checking based on order qty not the confirmed qty?

How can we restrict this.I thought logic to disable the changing of  qty manually.But there are cases to do partial delivery.How can this acheived.

Thanks,

Pradeep M