Invoice Custom Total

Invoice Custom Total

Hello,
I want to change columns Rate and Discount in the Invoice template and set it with custom data (charges and fees).
For this purposes I want to disable total calculation due to it spesific in my service.

So,
1. Is it possible to disable total calculation in Zoho Invoice?
2. If yes, it is possible to set it manually via REST API?

Thank you

Sorry for bad english