update magento currency rates using custom php file

I'm trying to use a custom file to update currency rates using cURL from my local bank and insert the data into the currency database table. 开发者_StackOverflow中文版Do I have to create a module to do that, or can I do that without creating a module? I intend to use cron too. Does anyone have any advice on how to achieve this, and are there any tutorials?

Thanks..

Best way to create custom mangento api as changing currency rates is not implemented in default magento api. Here is a simple tutorial that you can follow to implement the custom api http://www.magentocommerce.com/wiki/doc/webservices-api/custom-api