Reports :: Sum Values From Textboxes - DLookups On Report Group?

I have a report that returns timesheet info on employees. The group-by is on the employee, and the detail records are projects billed-to, including how much time billed to each project by that employee.

Parts of the detail line are accomplished by dlookups, and I was hoping to sum() these values on each employee/group, in the employee footer area.

Per the image, the circles show where I hope to show the sum'd value from text boxes indicated by the arrows...

In the group footer on employee I've set text boxes to:

Code:
=Sum(DLookUp("ProjectLeaveHours","qryTimeRpt_LeaveOnly"))

...basically taking the dlookup accomplished in the detail line and trying to sum() it... No luck.

Code:
=Sum([RADefaultHours])

...using the name of the control where the dlookup is accomplished prompts me to declare the value of the "RADefaultHours" - indicating the report text box control doesn't know what I'm talking about...

Code:
=Sum([Reports]![rptTimesheetReport]![RADefaultHours])

...trying the above again, but hoping to properly declare what is being sum'd... No luck.

...I saw some posts regarding setting "running sum over group" - and I tried that on the text box in the footer where the sum() is being attempted, but no luck.

Can I do this this way? Perhaps I need to set some other variable that is more agreeable than a 'textbox with a dlookup' to do the sum when grouping?