How to consolidate and return extensions

[xps350]

First of all: you should not STORE Total_Days_Extended in the project table. It is a derived value, that you should calculate and SHOW whenever needed. For that you use a query like:

SELECT tblProjects.ProjID, tblProjects.Base_Due_Date, Sum(Nz(tblExtensions.NumDay)) AS Total_Days_Extended
FROM tblProjects LEFT JOIN tblExtensions ON tblProjects.ProjID = tblExtensions.ProjID
GROUP BY tblProjects.ProjID;