VBA Error 'Subscript out of Range' - vba

Question

I am trying to create a copy of a large macro enabled (xlsm) file in xlsx format.
Sub Button1_Click()
Dim wb As Workbook
Set wb = Workbooks.Open("C:\original.xlsm")
Dim mySheetList() As String
ReDim mySheetList(0 To (ThisWorkbook.Sheets.Count) - 1)
Dim a As Integer
a = 0
For Each ws In ActiveWorkbook.Worksheets
mySheetList(a) = ws.Name
a = a + 1
Next ws
'actually save
Worksheets(mySheetList).Copy
ActiveWorkbook.SaveAs Filename:="ORIGINAL_COPY.xlsx" 'default ext
wb.Close
End Sub
I am getting subscript out of range error at following line:
mySheetList(a) = ws.Name

Answer 1

You are sizing the array with ThisWorkbook.Sheets but the loop use ActiveWorkbook.Worksheets. You need the same reference to avoid issues when multiple workbooks are opened.

Answer 2

You're using 4 different references to workbooks:
wb, ThisWorkbook and ActiveWorkbook are not necessarily the same thing. Furthermore, when you use Worksheets without prefixing it with a workbook reference, you're implicitly referencing the Activeworkbook. And, when you use Worksheets.Copy without any arguments, you're implictly creating a new workbook.
Currently, if ThisWorkbook has fewer sheets than original.xlsm, then your array will not be large enough to accommodate indexes larger than the count of sheets in ThisWorkbook. That is what is causing your out of bounds error.
I've adjusted the code. This will open the XLSM, copy the sheets, save the new XLSX workbook, and close the original XLSM, leaving the new XLSX workbook open.
Sub Button1_Click()
Dim wbOriginal As Workbook
Dim wbOutput As Workbook
Set wbOriginal = Workbooks.Open("C:\original.xlsm")
Dim mySheetList() As String
ReDim mySheetList(0 To (wbOriginal.Sheets.Count) - 1)
Dim a As Integer
a = 0
For Each ws In wbOriginal.Worksheets
mySheetList(a) = ws.Name
a = a + 1
Next ws
'Unfortunately, Worksheets.Copy isn't a function, so it doesn't
'return the workbook that it creates, so we have to execute the
'copy, then find the activeworkbook
Worksheets(mySheetList).Copy
Set wbOutput = ActiveWorkbook
'actually save
wbOutput.SaveAs Filename:="ORIGINAL_COPY.xlsx" 'default ext
wbOriginal.Close
End Sub

Answer 3

Why bother with all that looping?
Sub MM()
Dim sourceWB As Excel.Workbook
Set sourceWB = Workbooks.Open("C:\Original.xlsm")
sourceWB.SaveAs "C:\ORIGINAL_COPY.xlsx", FileFormat:=xlOpenXMLWorkook
sourceWB.Close False '// Optional
End Sub
The .SaveAs() method would be far more effective.
As mentioned in other answers, your issue seems to be with wb, ActiveWorkbook and ThisWorkbook being used interchangeably when they are actually different things.
wb is a workbook object that has been set to "C:\original.xlsm". It will always refer to that workbook unless you close the workbook, empty the object, or assign a new object to it.
ActiveWorkbook refers to the workbook that is currently active in Excel's forefront window. (i.e. The workbook you can see on your screen)
ThisWorkbook refers to the workbook in which the currently executing code belongs to. To quickly explain the difference:
Workbook A is the only workbook open, and has some code in to open another workbook (let's call it Workbook B).
At the moment, Workbook A is the ActiveWorkbook.
The code in workbook A starts running, workbook A is now the ActiveWorkbook and ThisWorkbook (because the running codes resides in this workbook)
The code opens Workbook B, which naturally opens in the forefront of Excel. Now Workbook B is the ActiveWorkbook and Workbook A is still the ThisWorkbook
Hopefully that clears it up a bit for you...