everything at our client is make to order. so if a client wants to order an item you need to be able to check how many items you can create from the BOM components. for example if a customer wants to buy 4 cars and it takes 4 wheels, 1 hooter and 2 windscreens to assemble a car. If you currently have 12wheels 2hooters and 6windscreens then the system should be able to tell you that you can only make 3 cars. how can one do this without having to create the car first?
BOMs - how to check how many BOMs you can produce
I assume that you want to base this on the sales order or an enquiry form. This is not a standard report/enquiry (but a common request) - you will need to develop this.