Excel 2013 VBA Error

Question

I am getting following error.

Compile error: The code in this project must be updated for use on 64-bit systems.

VBA CODE

Option Explicit

Private Declare Function URLDownloadToFile Lib "urlmon" _
Alias "URLDownloadToFileA" (ByVal pCaller As Long, _
ByVal szURL As String, ByVal szFileName As String, _
ByVal dwReserved As Long, ByVal lpfnCB As Long) As Long

Dim Ret As Long

'~~> This is where the images will be saved. Change as applicable
Const FolderName As String = "C:\Temp\"

It works fine in Excel 2010.

Thanks.

EDIT

Error I get is Ret Variable Not defined. Here's the rest of the code.

Sub Sample()
    Dim ws As Worksheet
    Dim LastRow As Long, i As Long
    Dim strPath As String

    '~~> Name of the sheet which has the list
    Set ws = Sheets("Sheet1")

    LastRow = ws.Range("A" & Rows.Count).End(xlUp).Row

    For i = 2 To LastRow '<~~ 2 because row 1 has headers
        strPath = FolderName & ws.Range("A" & i).Value & ".mp3"

        Ret = URLDownloadToFile(0, ws.Range("B" & i).Value, strPath, 0, 0)

        If Ret = 0 Then
            ws.Range("C" & i).Value = "File successfully downloaded"
        Else
            ws.Range("C" & i).Value = "Unable to download the file"
        End If
    Next i
End Sub

Answer 1

You must be running this on a 64Bit version of Office whereas previously you were using a 32Bit version.

To convert 32Bit calls to 64Bit you generally have to add PtrSafe to the function and convert some of the data types from Long to LongPtr (which is merely a larger datatype (see: http://msdn.microsoft.com/en-us/library/office/gg251378.aspx)

So the converted function would be:

Private Declare PtrSafe Function URLDownloadToFile Lib "urlmon" _
    Alias "URLDownloadToFileA" _
    (ByRef pCaller As LongPtr, _
     ByVal szURL As String, _
     ByVal szFileName As String, _
     ByVal dwReserve As Long, _
     ByRef lpfnCB As LongPtr) _
As LongPtr

Edit: Note if you want to be able to use this on both 64Bit and 32Bit versions of Office you need to use a preprocessor If statement so Office knows which function to use. Ie:

#If Win64 Then
    Private Declare PtrSafe Function URLDownloadToFile Lib "urlmon".......
#Else
    Private Declare Function URLDownloadToFile Lib "urlmon".......
#End If

Answer 2

MSDN reference

Complete error message: The code in this project must be updated for use on 64-bit systems. Please review and update Declare statements and then mark them with the PtrSafe attribute. All Declare Statements must now include the PtrSafe keyword when running in 64-bit versions of Microsoft Office. The PtrSafe keyword indicates a Declare statement is safe to run in 64-bit versions of Microsoft Office. Adding the PtrSafe keyword to a Declare statement only signifies the Declare statement explicitly targets 64-bits, all data types within the statement that need to store 64-bits (including return values and parameters) must still be modified to hold 64-bit quantities using either LongLong for 64-bit integrals or LongPtr for pointers and handles.

Add the PtrSafe keyword.