changing excel files with script

HI,
Let me start of as I am a newbie to programming, but I know enough of the basics to understand
Here is my situation, I’m building a website and I want to be able to download a pricelist (in excel format) of a website and increase the prices by approx 20 to 50% but keep it under the recommended retail price (RRP). Unfortunately the company updates there list every week or so. So instead of having to update my price list by hand every week i would prefer to just upload the file to the script and let it do all the hard work.
If possible can some one please type up the code for me. if not instruct me how to do it.
Also I don’t mind what ever language you guys would prefer, but if possible can it please be in VB

PLZ
It will be greatly appreciated
thankyou