a viral growth model (part 2)

Attached is an excel document made up of 2 pages. The first page is fully coded and works as required, on the second page is what i need doing. what were doing on the second page is taking the first page one one step further by allowing for new injections of customers at different times throughout the cycle each one therefore starting its own cycle which contributes to the total. Basically the top part of the second sheet (shown in blue) is the same as that shown on the first sheet, it works using the same formulas and the same input fields as that shown on the first sheet (all shown on the first sheet in deep red so when the formulas change on sheet one they effect the fields on sheet 2, if required it can all appear on one sheet). The second sheet needs to allow us to add further customers at different stages of the sequence (weve called these customer injections) and they then have their own viral build up which contributes to the total at the bottom in green . On the second sheet where it says advertising injections, the calculations that are done are again based on the same input fields as that shown on the first sheet in red so when they change the figures here change as well, all except the 'cust' field which needs to be added manually in the red rows for each of the seperate customer injections. There should only be one entry on each of the red rows. on the first 2 advertising injections shown i have manually done the math for the first few calcualtions and the total at the bottom in green however all of this needs to be automated. We need to be able to add new 'advertising injections' section by clicking the black button (or something similar) which will work the same as those currently shown. you can read about how the viral growth model works here: [login to view URL] Finally we need a new field adding to the first page, this will be called 'cust churn rate' , this will effect each of the column totals.