Set Analysis Sum Across Dimension

[erikzions]

I have a table with a date dimension.  I need to sum the previous quarters balance.  I have a field for the previous quarter.  I am having a hard time getting my set analysis to sum a previous date in the current dates dimension.  I have tried many things.  Below are two attempts.  I must be having a brain cramp because I know I have done this before.  Any help?

sum({< [As of Date] = {PreviousQuarter} >} [Balance])

also tried

sum({< [As of Date] = P({< [As of Date] = {'=PreviousQuarter'} >}) >} [Balance])

Date	Previous Quarter	Balance	Previous Quarter Balance
Sep 17	N/A	50	N/A
Oct 17	Sep 17	75	75
Nov 17	Sep 17	100	75
Dec 17	Sep 17	125	75
Jan 18	Dec 17	150	125
Feb 18	Dec 17	175	125

[Digvijay_Singh]

PFA