If/then statement that checks multiple columns then averages?

I'm working on consolidating a data set right now that has 55 subjects with multiple variables per subject to enter into SPSS for regression analysis. I have multiple data points per variable per year, and what I'm trying to do is get the averages for each type of variable per year per subject.

Each year is set to start at 0, and I have 8 variables (phosphorus, nitrogen, dissolved oxygen....etc) that are all text fields. Is there a way to write a function (or macro, just less familiar with those) that has Excel check column A for what year, then column B for which variable, to get one cell that averages the phosphorus total within that one year?

Since I have so many subjects, and each subject has 40 years of data, I'm trying to not do this by hand if at all possible.

Huge thanks to whomever can help with this! Screenshot of example data is below.