This is what I have so far but, it just queries the DB. No math.
declare @Date DATE --Business Date--
set @Date =(select (CONVERT(VARCHAR(10),(select BUSINESSDATE from XXX_YYYYY.dbo.T_REF_PRICE_DATE where ID = 1),101)))
declare @Date1 DATE --Business Date--
set @Date1 =(select (CONVERT(VARCHAR(10),(select PREVIOUSBUSINESSDATE from XXX_YYYYY.dbo.dbo.T_REF_PRICE_DATE where ID = 1),101)))
SELECT XXXInstrumentID,XXXTransactionID,BusinessFunctionSource,TransactionDate,TransactionStatus,XXXPortfolioID,XXXPortfolioCode,PortfolioName,XXXLeadCashPortfolioID,InstrumentDescription,SettlementDate,XXXCounterpartyName,Quantity,GrossAmountInPortfolioCurrency
from SQLOpenDoor.Services.TransactDB where TransactionDate = @Date
and TransactionStatus = 'Active'
select distinct a.EvaluationDate, a.XXXPortfolioID,a.XXXPortfolioCode,a.PortfolioName, a.XXXInstrumentID,a.InstrumentDescription,a.TotalQuantityNominalAmount,a.MarketValueInCAD
from SQLOpenDoor.Services.Inventory_v6 a
JOIN SQLOpenDoor.Services.Services.Inventory_v6 b ON a.XXXPortfolioID = b.XXXPortfolioID and a.XXXPortfolioCode = b.XXXPortfolioCode
where a.EvaluationDate = @Date
and b.EvaluationDate = @Date1