Could you clarify what you mean by qualifying the ranges (my formal programming training is ridiculously out of date)?
Right now I have this and it still is giving me a value of zero. I changed a couple other things as well to help me debug:
Dim eng_hours As Double
Dim maj_group As Range, bill_summary As Range, mtd_ttl_hours As Range
Set maj_group = Range("C:C")
Set bill_summary = Range("D:D")
Set mtd_ttl_hours = Range("E:E")
eng_hours = Application.WorksheetFunction.SumIfs(mtd_ttl_hours, maj_group, bill_summary, "ENG", "LABOR")
Debug.Print eng_hours