Build a Website based on a detailed macro driven excel model

I have a very powerful spreadsheet with 9 tabs that I want converted to an interactive website for financial planners to demonstrate live to their clients. It has a series of macros that need to function seamlessly in the background like they do in Excel. I will be building additional tabs and functionality over time and will need to edit/upgrade the website easily - either myself or with your help (if the upgrades are major) The software will need to collect revenue on a monthly subscription per user basis and should permit the user to create, save and load encrypted models into the current iteration of the software. The interface is currently quite flat (it is a spreadsheet) so you should allow time and have the skill to upgrade the interface to a contemporary look. it is possible that we may want to upgrade the interface to have 6 to 8 major tabs along the top some of which have 3 or 4 sub tabs on the left hand side. On the right hand side a series of tabs would permit the display of graphs. The primary excel calculation engine is relatively small with only 200 rows and around 130 columns however there are a series of graphs and tabs which display data from the primary calculation tab or provide additional input fields - nothing more than 100 rows by 20 columns and with no difficult calculation. The primary calculation engine has thousands of macro calls. The macros are simple VBA but they must function perfectly and in real time. There is a high degree of mathematical precision needed in this project due to the precise financial calculations that must be performed.