Hello Govind,
You may refer to the below link for the list of Web Services API available in 1408.
Web Service APIs in SAP Business ByDesign 1408 - August 2014
For more details about exchange Rate API.
Inbound Service Interface (public)
Now as far as I understand that you can't just give the URL of third party and automatic upload the exchange rates. But you can use this webservices API to maintain the exchange rates.
To summarize, you need to write custom logic to read the exchange rates from 3rd party URL and then upload it in the required XML format via the ManageExchangeRates API.
Hope this helps
Thanks
Parveen Kumar