Line item confirming issue

We have a probelm with TAPA/TAN orders confirming the product. The TAPA line may "confirm " the entire amount requested , but the TAN line only confirms what is available even with the complete button checked on the order, therefore, if the sales person doesnot notice that the TAN line is not fully confirming, we may ship partial loads of orders. this is a manual process that is causing problem to the customers. How to resolve so that both item line confirm or donot confirm. Plz help.

Thanks!