Hi there. I would be happy to build your ROI calculator for you. I have previously made a calculator that appears on a leading yacht charter website that uses google maps to allow the client to draw their charter route and then allows input of variables for fuel cost, etc, and calculates the cost for fuel and likely carbon emissions for them.
Please send me a message if you'd like to chat more about the project and consider me suitable for it. I am online for most of each day so I'll reply asap.
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Website Applications Developer - PHP/MySQL / HTML/CSS/JQuery/AJAX/JS / SEO - 10 years experience building front-end and back-end for a global yacht charter company. I was the sole developer for 90% of that time. I also built my own online yahtzee (dice game) community with real-time games/chat which is still fairly popular today.
Some of the projects I have completed: booking systems, search/sales/accounts/management/CMS tools, file upload handling, image processing (sizes, adding text, grafting two images etc etc), on-the-fly PDF creation, automated emails with files attached, web-scraping (with/without login spoofing), email scraping, financial/accounts calculations/reports, complex management reporting, proposal creator, editing responsive designs, real-time chat and AJAX-based games, community forum, paypal API, google maps, calculators, etc etc.