How to update net_total price in Custom module in Estimated Quotation?


I have created custom module estimated quotation under selling module.

In that First i have added Item table after , then am adding labor expenses and logistics expenses then updating total price.

Then am calculating taxes , so it is getting calculated on the basic item table price. Means whatever value was added in field name total like labor expenses and logistics expense. that final value is not taking in tax calculation input.

I think tax calculation happens on field name net_total. but that is not visible in front-end and if we are updating net_total by jquery that is also not working.

Please somebody tell me solution. Last 4-5 days i m working in this issue only but still not resolved.

In screenshot 1 → all labor expenses and logistics expenses are added into the field name total and is working fine.
In screenshot 2 → but Grand total is still showing the only all item total. that is we can update through JS also.
In screenshot 3 → When I calculate tax on existing total , it is not taking total value , it is only taking the item price count only , whatever value added after labor and logistics expenses that value it is not taking. after tax calculation it replaces value also.