Controls on sales order and invoicing of 2k( components products

Dear All:

We deals in many products which are sold in combination( these are called 2K products) .We want to develop a check /control in the system that does not allow to enter such items in isolation i.e. singly at the time of entering sales orders and making invoicing of such items.

Currently sales order can be entered for any component and similarly component can be invoiced which creating problems for us as customer is not willing to accept such products without proper combination.

please help to build such control as requested above and guide us accordingly.

ATA