UK Accounting Excel File

I require the following work completed to this excel file:

1. When a client right clicks they are able to add new income and or payment rows but with the addition that the new rows automatically follow the calculations of the appropriate fields calculations for income or expenses already existing.
2. In row 40 the VAT should automatically calculate.
3. In rows 47 & 48 I am open to suggestions as to adding an automatic calculator that depending upon a dropdown selection of the write off percentage the fields should automatically calculate/recalculate.
4. The balance sheet and P&L sheet should also be automatically populated.

I am open to suggestions on this matter but I wish for the most simplified automated system so that small businesses are immediately able to understand how to use this excel file and use it to hold a quick and simple financial snapshot of their accounts.