Google Spreadsheets™ is a great asset to use instead of Microsoft Excel. It supports collaboration, functions in cells, and has a great add-on system to extend its functionality. 

Usually, when there is a need to calculate currency rates, the built-in Google rates are what everybody is using, but that is not a good solution when your enterprise is in Hungary. The Hungarian National Bank makes its currency rates available publicly on a daily basis and even has an API to reach these rates from code. However, the API uses a SOAP-based approach which is not available anymore in Google add-ons. It seems Google decided that SOAP has reached its end of life, at least in their platforms.

This add-on solves the issue using the Google App™ Scripting engine to create the missing link.