google sheets – offset table extension

I build a spreadsheet that shows the bonuses granted to an employee that are acquired and distributed over a period of three years.

Easier to see the example:

In the first sheet, everything is fine, but for each new year, I have to manually place the {x / 3, x / 3, x / 3} table formula in the good year that the acquisition should begin.

I want it to work like the second sheet, where I just add new data to the green section, and the 3 payments appear from the next year. In column C, I calculated the offset where the payment should begin. I just need a way for the matrix formula to start expanding at this offset.

Note that sometimes there is more than one grant per year, if that counts.