Manufacturing operation as Optional Selection

Hi,

I have scenario here while making the SFG i need to complete operation sequence from 10 to 50, But this particular SFG while manufacturing needs to repair the product like correction after or before the finish, out of 100 product 40 product needs to repair,Now i need to add the material and resource for capturing the repair process at work order level by entering manually, is there any other way needs to keep the operation as optionally, instead of manual entry needs to select and complete the operation at same time cost needs to be roll up