Conversion Calculator (website already built)

I have a conversion calculator on one of my websites, it is very simple. The user inputs a number and then the calculator works out the conversion and displays the result on a [login to view URL] page. The website is totally finished in design, the pages are already styled (CSS) All I need is for someone to make the conversion calculator work correctly. Currently it is outputting the wrong results. I would also like to add more countries into the converter, you should also do this. The page must be 100% secure and NOT vulnerable to injection attacks. I have a full table of the conversion data available to me that I will show you. This is a quick and simple job as the site and pages are already 100% built. I just need someone to fix the calculation. The calculations are always static, so it's not complicated. You must have a lot of experience in web design and coding and capable of fixing this within a day. PM me for the website url - as the website is currently live. I expect very low price range, as this is a very easy job. Thanks and Good Luck!