Compare average before a date to the average after the date

I have two tables. One has name & date. The other has name, date, score.

I need to compare scores before that data to scores after.

So, somehow, from what I have (listed on one page on the attached sheet) I need something like:

Name Pre score Avg Post Score Avg

Mr A ? ?
Mr B ? ?
Mr C ? ?

Ideally I'd like to be able to choose how many pre & post scores to include :-)

Thanks,

Steveexcelscores.xlsx

The avarage (per month) is counted by a pivot table.

See the attached file.