Framework Purchase Orders

Our SAP system is set up as: Framework LIMIT PO's (B) do not have a quantity, Framework (K) DO have quantities (qty of 1).

When we invoice against a Framework limit we can enter invoice after invoices after invoice.

When we invoice against a Framework (K) there is a quantity of 1 so we have to invoice with a percentage of the total, i.e., total PO is for $50,000 and we invoice for $6400.00 so we have to manual calucalate the percentage (0.128) and invocie a quantity of 0.128.

Is it possible to set up Framework (K) without a quantity?

Thank you, Sandra