How to use formulas to stagger cash flows into a portfolio?

I'm currently trying to build a portfolio of cash flows which includes 10 assets. 2 assets will be bought each year. For simplicity's sake, lets say the cash flows from year 0-10 are simply 0, 1, 2, 3, etc. I'm trying to use a roundup function and an offset function to return the cash flows so that the cash flows are always starting at Year 0. So, for Year 1, the first two properties would have 1 for cash flow. The next year, the first two properties would show year 2 cash flows and the second two properties would start back at 1 one. The result would look like this:

0123456789 0123456789 0012345678 0012345678 0001234567 0001234567 0000123456 0000123456

I am currently using a ROUNDUP function to layer in the cash flows and an offset to pull the cash flows in. The formula looks like this:

Number of assets: 25 Number of assets per year: 2

=IF(Year>(ROUNDUP(Asset1/AssetsPerYear,0)-1,OFFSET(Cashflows@Year0,,Year,1,1),0) or (with numbers included) =IF(1>(ROUNDUP(1/2),0)-1,OFFSET(0,,1,1,1),0)

My problem is the cash flows for assets purchased in the second year are pulling in Year 2 cash flows. I know my offset is to blame but I can't think of a way around it. My results look like this:

0123456789 0123456789 0023456789 0023456789 0003456789 0003456789 etc.

Is there an easy solution to this problem? The file I'll be making will be quite large and I'd like to keep the formulas as simply as possible. Thanks for any solutions you could offer!