Solving for IRR Based on Irregular Cash Flows

Hi guys,

I'm trying to solve for IRR (let's say 20%) based irregular cash flows to the sponsor - essentially trying to find out what cash to sponsor is required to arrive at an IRR of 20%. So at close, the sponsor contributes $100 of equity. In a 10-year project, I know for sure at year 1 the project will generate 0 cash flow. Then in years 2-5, the project generates $1 of cash annually (after all expenses) for the sponsor. From years 6-7, the project generates $2 of cash for the sponsor.

How do I find out the amount of project cash flows required in the last three years to give the sponsor a 20% IRR? Is there a dynamic way in excel to solve for this as there is zero cash year 1 and irregular cash flows between years 2-7?

Thanks for your help.