If Condition in expression is not working as expected

[samp]

Below expression in if condition is giving wrong results for QTD and MTD  but the YTD and default result is correct, QTD and MTD is giving results always the same but still wrong.

if I go for individual expressions the results is always correct for YTD,QTD, MTD and Default , 

if(Time='YTD',Sum( {<Date={">=$(=YearStart($(vMaxDate))) <=$(=$(vMaxDate))"}, Time=>} [ Value]),
if(Time='QTD',Sum( {<Date={">=$(=QuarterStart($(vMaxDate))) <=$(=$(vMaxDate))"}, Time=>} [ Value]),
if(Time='MTD',Sum( {<Date={">=$(=MonthStart($(vMaxDate))) <=$(=$(vMaxDate))"}, Time=>} [ Value]),
Sum({<Date={">=$(=AddYears(YearStart(Today()),-1)) <=$(=AddYears(YearEnd(Today()),-1))"}, Time=>} [ Value]))))

Appreciate your help.

[samp · Accepted solution]

The below expression using GetFieldSelections (Period) is fixed my problem in place of If condition or Pick match.

if(GetFieldSelections (Period)='YTD',Sum( {<%Date_Num={">=$(=Num(YearStart($(=$(vCOGSMaxDate))))) <= $(=$(vCOGSMaxDate))"}, Period=>} [COGS Value]),
if(GetFieldSelections (Period)='QTD',Sum( {<%Date_Num={">=$(=Num(QuarterStart($(=$(vCOGSMaxDate))))) <=$(=$(vCOGSMaxDate))"}, Period=>} [COGS Value]),
if(GetFieldSelections (Period)='MTD',Sum( {<%Date_Num={">=$(=Num(MonthStart($(=$(vCOGSMaxDate))))) <=$(=$(vCOGSMaxDate))"}, Period=>} [COGS Value]),
Sum( {<%Date_Num={">=$(=Num(AddYears(YearStart(Today()),-1))) <=$(=Num(AddYears(YearEnd(Today()),-1)))"}, Period=>} [COGS Value]))))