Get the data from the web to Excel Web App

I have a folder on OneDrive/SharePoint with many Excel files, that need to be daily filled with the table of history of foreign exchange rates. Files would be used by users thru the web app.

I have two possible sources of FX rates: 1) rest api, 2) xls or csv from the website of central bank.  

What are the possibilites to automate it (without using desktop client)?