One of my clients needs to pull customer data from a web service periodically. The data itself is provided as CSV files via javascript postbacks, as is most of the navigation within the service's website. 

Right now, the worst bottleneck in the entire system is the need for a human to log into the web page, navigate to the download page, and manually add the downloaded file to the rest of the system. 

Can the process of downloading files via postback be automated? (Say for example via a shell script that can be run via cron?)

If so, what would you recommend as the most appropriate tool for doing so?