Add column to invoice as part of calculation

Hello there, is it possible to add for instance, a column in the invoice template for exchange rate calculation? I would like to add this after the Qty and amount columns so that it calculates to get to the final invoice amount? Hope this makes sense.

this is not possible.
but you can directly enter calculations in the Unit price column which will help you arrive at the total amount equalling the exchange rate value.
this guide will help you understand better. Perform calculations in number fields | Manager
for example, if the unit price is 135 and the exchange rate is 15, you can simply enter 135*15 in the Unit price column.