Excel Financial Model update

We have an existing excel based financial model, which we need modifying. We do not want to start from scratch, I repeat, we do not want to start from scratch, we simply want additional functionality building into the model.
Additional functionality includes the following;

On our original financial model, the cost hypothesis for some of our expenditure is the same for yr1, Yr2, and Yr3. This as you know is incorrect as expenditure does not stay the same 3 years in a row. We therefore need to include an algorithm that will automatically increase the expenditure each year by a variable input

I need to work out our staffing levels by working backwards from the revenue. I need you to calculate the 'revenue per employee' ratio based on our increasing turnover. This RPE needs to reflect the benchmark ratio of similar sized start-up tech companies. Once we have the benchmark we can work backwards from our revenue and work out how many staff we should have at any given time. I need to be able to easily include these new staffing levels into our cost hypothesis under the relevant job sub headings