Autofill error on Excel VBA code - excel

Question

trying to work the VBA autofill function (end of code block) but I am running into an error everytime I try the execute the code. I get "Autofill method of Range class failed". Can someone help me out here? Searched google but nothing works. Probably overlooking something small. Thanks in advance for the help.
Sub UpdateLAB() '---> still need to work on this
'author: css
Dim SalesBook As Workbook
Dim ws2 As Worksheet
Dim wspath As String
Dim n As Integer
Dim FirstRow As Long
Dim LastRow As Long
Dim LastRow2 As Long
Dim sourceCol As Integer
Dim RefCellValue2 As String
Dim ps As String
Dim Platts As Workbook
Application.Calculation = xlCalculationAutomatic
Set SalesBook = Workbooks("ALamb.xlsm")
Set ws2 = SalesBook.Worksheets("US LAB Price")
wspath = "C:\Users\scullycs\Desktop\P&O\Platts Data\Platts 2016.xlsm"
FirstRow = ws2.Range("B4").Row
LastRow = ws2.Range("B4").End(xlDown).Row + 1
LastRow2 = ws2.Range("c4").End(xlDown).Row
sourceCol = 2 'refers to the column your data is in
For n = FirstRow To LastRow
RefCellValue2 = Cells(n, sourceCol).Value
If IsEmpty(RefCellValue2) Or RefCellValue2 = "" Then
Cells(n, sourceCol).Offset(0, -1).Copy
SalesBook.Worksheets("Control Page").Range("C8").PasteSpecial (xlPasteValues)
Else
End If
Next n
ps = SalesBook.Worksheets("Control Page").Range("C9").Text
Set Platts = Workbooks.Open(wspath)
Platts.Worksheets(ps).Activate
Range("A13").End(xlDown).Select
Selection.Offset(0, 11).Select
If Selection.Value = "" Then
MsgBox ("Platts data does not exist")
Platts.Close
Else
Selection.Copy
Set SalesBook = Workbooks("ALamb.xlsm")
SalesBook.Worksheets("US LAB Price").Range("b1").End(xlDown).Offset(1, 0).PasteSpecial (xlPasteValues)
'this is where I get the error
SalesBook.Worksheets("US LAB Price").Range("c4").AutoFill Destination:=Range("C4:C" & LastRow2), Type:=xlFillDefault
Platts.Close
End If
End Sub

Answer 1

Most probably your ranges are not overlapping OR range is too big. In case you want to refer, link.
Check the value of LastRow2.
Make sure the fill range is from same sheet to make them over lapping. To do so break your statement into simple steps. Later you can combine.
Will suggest to break down the statement into
Set SourceRange = SalesBook.Worksheets("US LAB Price").Range("C4:C4")
Set fillRange = SalesBook.Worksheets("US LAB Price").Range("C4:C" & LastRow2)
SourceRange.AutoFill Destination:=fillRange, Type:=xlFillDefault