Just by looking at it seems like this is just an SQL join (or in Coldfusion just a QoQ) but I ran into a complication because one query contains SQL arithmatic and other doesn’t. Obviously SQL JOIN is also out of the picture.
So this is my solution,
<cfquery name="q1" datasource="myDataSource"> SELECT T1.ItemNo, T1.UnitSize, T2.uCount, (T1.UnitSize * T2.uCount) AS ItemUsedAmt FROM TABLE1 AS T1, (SELECT DISTINCT ItemNo, SUM(UnitCount) AS uCount FROM TABLE2 WHERE PO = '#ARGUMENTS.PO#' GROUP BY ItemNo) AS T2 WHERE T2.ItemNo = T1.ItemNo </cfquery>
(my answer is inspired with internet research and I wish i wrote down the website that lead me to this solution.)