Forms :: Using DSum In Text Box

I have a volunteer information database, and I am working on the form that will show the details of each volunteer's hours worked, among other things.

I've attached screenshots of a more or less final version of the Relationships (I've tweaked it a little in the last day or so but nothing life-altering), the section of the form in question, and a query I wrote (probably incorrectly) that does return hours on a given month sorted by NameID, which is useful, but doesn't put the information into fields like I'd imagined I could. If I can't figure out how to make what I'd like work, I guess I could just put a subform that displays the results of the query, but I'd rather do it another way.

I tried this in the controls for each field:

Code : DSum( [tblHoursWorked]![MonthWorked] , "MonthWorked='November'")

Obviously switching out the months, but I'm getting the response of #Name? in each field. No syntax error so I'm not sure if I have something configured incorrectly in the text boxes or if there's a problem with the function.