Data mining a third party website.

I need a program or script to mine data from a retail website that have couple thousands of products at most. For the data results, I need to be able to perform custom searches on the terms I specified. The data mined has to be up to date, and the latest change will need to be displayed so I can see it clearly. When bidding, please describe your approach, requirement, and time frame required to finish this project. Thank you.