what is wrong with this?? Errors out at the autofill... 

CurrentWB.Worksheets("Data Processing").Range("I2").Formula = "=IF(D2=0,IF(E2=0,"",E2),D2)
    With CurrentWB.Worksheets("Data Processing").Range("I2")
        .AutoFill Destination:=Range("i2:i" & LastRow)
    End With
Have tried this:

CurrentWB.Worksheets("Data Processing").Range("I2").Formula = "=IF(D2=0,IF(E2=0,"",E2),D2)"
CurrentWB.Worksheets("Data Processing").Range("I2").Copy
CurrentWB.Worksheets("Data Processing").Range("I2").Range(Cells(2, 2), Cells(Endrow, 2)).PasteSpecial (xlPasteFormulas)
and this:

    With Worksheets("Data Processing")
     .Range("i2:i10").Formula = "=IF(D2=0,IF(E2=0,"",E2),D2)"
     .Select
     .AutoFill Destination:=Range("K4:K" & LastRow), Type:=xlFillDefault
    End With
Incredibly frustrating as I am sure it is something stupid.... we all have our moments....