Also worked in below way
Bgt Avg YTD = = VAR Purch_curr = MAXX('GRIP','GRPI'[Purchase curr]) RETURN( (CALCULATE(AVERAGEX('FX Rates','FX Rates'[[Bgt Avr YTD]),DATESYTD('Reporting date'[Date]),'Currency'[Currency]= Purch_curr)) ```