Trying to get a rolling average

trying to use the below to create a rolling average measure

this measure is in the same table as the revenue,

the revenue line gets highighted it seems to think it should be a sum or average. But if I do that it still doesnt give me the right value it seems to just give me that months value (on my graph by month)

Rolling 3m =
AVERAGEX(
WINDOW(
-2,REL,
0, REL,
SUMMARIZE(ALLselected(date_info),date_info[year_code],date_info[Month],
date_info[period_code]),
orderby(date_info[period_code],ASC)),
[Gross Revenue])