Last 3 month average

Good day,

I am looking for a measure where i can average the last 3 months revenue, excluding the most current month. I want to compare July revenue to an average of April, May & June revenue. I do have a separate date table.

the measure i tried was:

Revenue 3 Mo Rolling Avg = CALCULATE([TotalRevenue],DATESINPERIOD(DateDim[Date],LASTDATE(DateDim[Date]),-3,MONTH))/3

This measure gives me the average for May, June and July. Any ideas?

Thank you!