Excel loop stops working - excel

Question

I've built an Excel Macro which takes the first sheets from all XLS files in a selected folder (including XLS files in any sub-folders) and copies the sheets onto a single sheet in a new Workbook. The code seems to work fine for the most part and I intend to use it to merge thousands of Excel sheets into a single file.
However the problem is that the loop just stops working at some point, with no errors raised. Sometimes it's a couple of hundred files, sometimes more. But the process seems to be unreliable and I can't tell why.
This is my code (I call the Merge macro which in turn calls the DoFolder Sub):
Sub Merge()
Dim FileSystem As Object
Dim HostFolder As String
HostFolder = "C:\XLSfiles"
Set FileSystem = CreateObject("Scripting.FileSystemObject")
DoFolder FileSystem.GetFolder(HostFolder)
End Sub
Sub DoFolder(Folder)
Dim unusedRow As Long 'used for writing the file path info before each copied sheet
Dim path As String, ThisWB As String, lngFilecounter As Long
Dim wbDest As Workbook, shtDest As Worksheet, ws As Worksheet
Dim Filename As String, Wkb As Workbook
Dim CopyRng As Range, Dest As Range
Dim RowofCopySheet As Integer
RowofCopySheet = 2 ' Row to start on in the sheets you are copying from
ThisWB = ActiveWorkbook.Name
Set shtDest = ActiveWorkbook.Sheets(1)
Dim SubFolder
For Each SubFolder In Folder.SubFolders
DoFolder SubFolder
Next
Dim File
ActiveWindow.WindowState = xlMinimized
For Each File In Folder.Files
' Operate on each file
unusedRow = Cells.SpecialCells(xlCellTypeLastCell).Offset(1, 0).Row
If Not Filename = ThisWB Then
Set Wkb = Workbooks.Open(File)
Set CopyRng = Wkb.Sheets(1).Range(Cells(RowofCopySheet, 1),Cells(ActiveSheet.UsedRange.Rows.Count, ActiveSheet.UsedRange.Columns.Count))
Set Dest = shtDest.Range("A" & shtDest.UsedRange.SpecialCells(xlCellTypeLastCell).Row + 1)
CopyRng.Copy Dest
Wkb.Close False
End If
Cells(unusedRow, 1) = File
Application.StatusBar = File
Next
Range("A1").Select
End Sub
What am I missing?

Answer 1

Try this:
Instead of copying ranges, you can simply set their value
Do not use Cells when working with multiple sheets; always explicitely state the object/sheet whose Cells you like to address
Sample that worked for me:
For Each fi In f.Files
If InStr(1, Right(fi.Name, 5), ".xls") > 0 Then
Set Wkb = Workbooks.Open(fi)
Set ws = Wkb.Sheets(1)
rowCount = ws.UsedRange.Rows.Count
colCount = ws.UsedRange.Columns.Count
ranString = shtDest.Cells(curRow, 1).Address & ":" & shtDest.Cells(curRow + rowCount, colCount).Address
Set ran = ws.Range(ws.Cells(2, 1).Address, ws.Cells(rowCount, colCount).Address)
Set destRan = shtDest.Range(ranString)
destRan.Value = ran.Value
curRow = curRow + rowCount
Wkb.Close False
End If
Next fi
It may look a bit long-winded building a range string first, but it made debugging easier.