How to sum based on a specific cell

I'm doing an excel for quarterly results where I need to add the results on a Year to Date basis.

So let's say I have

1Q2020 2Q2020 3Q2020 4Q2020  1Q2021 2Q2021 3Q2021 4Q2021         3Q2021  YTD

10           20          30          40           15           25          35         45                                ?

I already have a cell (bold letters) where I input which quarter I want to see, so I need that the YTD adds the numbers for that quarter and ONLY the previous quarters of that same year... in the example above, in bold, there's 3Q2021 so I need the YTD to add 15+25+35 once I input 3Q2021 on the bold cell.

I thought about a formula where based on the bold input it adds 1 cell below for 1Q, the cell below and the previous one for 2Q, the cell below and the two previous ones for 3Q, etc... But I couldn't figure a formula that lets you add above or below cells based on a fixed cell.

I thought something like the index+match formula but instead of giving out a certain cell above/below, I need this to ADD/SUM certain cells above/below, not just give out a single cell.

Any ideas? Thanks!