Magento2 : How Can I Update My Custom Fee While I Update Qty From Admin New Invoice Section

Question

I have create one module to add custom fee to order product wise , for eg . 1 product = 10 , so 5 product = 50 , and custom fee is working fine in all section like checkout, order, Invoice

now my requirement is i need to update my custom fee when i update qty in admin new invoice section as per above screenshot.

I want if i update qty to 0 for last 2 product than that 2 product custom fee should not be add.

If any one have idea than please tell me.