I got it to work, Played around with the syntax, all is good! thanks for the help.

Here is my answer:

NetPosition: (SELECT SUM(T2.TradePosition)


FROM tblPositions AS T2
WHERE T2.ClientID = T1.ClientID
AND T2.InvestmentID = T1.InvestmentID
AND T2.MonthlyDate <= T1.MonthlyDate)