Delay the completion of supplies based on which OP they are required for

I hope someone has come across this scenario before.

I have a product structure that has some components connected to a later OP in the routing. This is because I don’t need the parts until, say, OP 30 or 40.

However, MRP plans ALL the components as due on the start date of the shop order, completely disregarding the fact that I don’t need some components until the third or fourth OP, which may be weeks after the start of the shop order.

Does anyone know how to get MRP to schedule these supplies as due after the start of the shop order and actually due when that OP they are connected to is scheduled to start?

Be grateful for any views. Still using Apps 9.

Thanks.