Sales order item amount

hi all.
i create custom field service_charge type = float in sales_order item. and i want to user input service_charge price by item. how can recalculate amount of item when user input or change value in this field.
by amount = amount + service_charge
I’am try to insert custom scrirpt but amount field of item recalculate change when save only. not recalculate amount when change value on item.

i want to recalculate amount same as qty or rate?

help me pls.

In the search bar, type in “New Custom Script”, enter “Sales Order” for the doctype, and create a custom script.

There are many examples of scripts in this forum, for example Computation of total quantity in delivery note form - #3 by architgarg1990

thank’s crafter
I’am will try this

i’m try this but when change value in field service_charge and enter not show new total amount in row.
total amount in row is change when save only

i wan’t to see new total amount in row when change value in field service_chare before save.

help me pls.

Post your code. This may help someone provide an answer.