function purpose not clear
I don't see what you plan to do but this gives no error:
Function dup1()
If ([Report_Operator production report]![Work Type] = "Dup-1") Then
dup -1 <= 0
Else
dup1 = Int(Sum([job completed time] - [job start time] - CDate("0:0:" & DatePart("s", [job completed time] -...