In a chart table, average over previous 3 months for each row

[maxattar]

Hi experts,

Can you help me achieve the following : 

I want to calculate the average score over a period of 3 months for each row of a table containing the age of the player at which the score was done, the date of the score and the score itself.

How could I achieve such thing (in the sheet itself or in the load script) not using As Of table (which I can't use because of what I want to do next : show each of these average scores for each player in a bar graph where the dimension is not the date of the score but the age at which the players achieved the scores).

I managed to do it for the last 3 months before today using the following measure : 

{<Score_date={">=$(=AddMonths(Today(),-3))"}>}Avg(Score) but can't do it for all of the scores before this period.

Thanks a lot !