copy of header condition from inquiry to sale order

Dear Guru

I have the following issue:

I have a condition header price in inquiry that is managed as splitted in all the items of the inquiry.

Now happens that when I create the sale order from the Inquiry, if I take less items and not all the items of the inquiry, the condition header changes according to the items copied in the order.

I don't want this behaviour! I need that the value of the header condition keep the original one of the inquiry even if i have less items. what will change is the value of every single item in the sale order.

How can I obtain it?

regards