Data extraction from websites

I need a programmer developer to write me a script/programme that can extract product data from a website at the click of a button, or even better if it could be on a timer/schedule. once per day at a specific time. There are approximatly 2000 products that will need to be extracted on a daily basis, so it is vital that i own this programme and it works without any errors at all! I will need to see it demonstrated and tested out on my system to make sure that it fully works without any errors before payment for the work is finalized. If the script works then there is the possibility that i will need a programme designing for 3 more websites.