64位Excel VBA中URLDownloadToFile函数声明报编译错误的原因

该编译错误和你写的64位兼容API声明本身的语法无关，核心触发原因是：你将API声明、模块级常量的代码放在了某个已有过程（Sub/Function/Property）的代码块内部，而非模块的通用声明区域（所有过程之外的模块最顶部）。

VBA语法有明确约束：

• Declare形式的外部API声明、模块级Const常量定义，都属于模块级代码，必须写在所有自定义过程的代码块外部，不能嵌套在任何Sub/Function/Property的首尾语句之间。
• 当VBA编译器在过程内部读到仅允许出现在模块级的声明语句，或是在某段过程的End Sub/End Function/End Property语句后读到非注释的声明/可执行代码，就会抛出你看到的报错。

• 打开VBA编辑器定位到当前代码，检查是否误将API声明段粘贴到了其他已有宏的Sub xxx()和End Sub之间。
• 将从#If VBA7 Then开始的条件编译API声明块、4个公共常量定义的所有代码，剪切到模块最顶部，紧接在Option Explicit语句下方，所有自定义过程的上方。
• 确认模块内代码的层级顺序符合要求即可正常编译，正确结构参考下方代码示例：

Option Explicit

' 模块级API声明段（所有过程外）
#If VBA7 Then
    Private Declare PtrSafe Function URLDownloadToFile Lib "urlmon" _
      Alias "URLDownloadToFileA" ( _
        ByVal pCaller As LongPtr, _
        ByVal szURL As String, _
        ByVal szFileName As String, _
        ByVal dwReserved As Long, _
        ByVal lpfnCB As LongPtr _
      ) As Long
    Private Declare PtrSafe Function DeleteUrlCacheEntry Lib "Wininet.dll" _
      Alias "DeleteUrlCacheEntryA" ( _
        ByVal lpszUrlName As String _
      ) As Long
#Else
    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
    Private Declare Function DeleteUrlCacheEntry Lib "Wininet.dll" _
      Alias "DeleteUrlCacheEntryA" ( _
        ByVal lpszUrlName As String _
      ) As Long
#End If

' 模块级常量定义（所有过程外）
Public Const ERROR_SUCCESS As Long = 0
Public Const BINDF_GETNEWESTVERSION As Long = &H10
Public Const INTERNET_FLAG_RELOAD As Long = &H80000000
Public Const folderName As String = "c:\temp\"

' 自定义宏过程
Sub downloadImages()
    Dim i As Long, ret As Long, sWAN As String, sLAN As String
    
    With Worksheets("Sheet1")
        For i = 2 To .Cells(Rows.Count, "B").End(xlUp).Row
            sLAN = folderName & .Cells(i, 1).Value & ".jpg"
            sWAN = .Cells(i, 2).Value
            ' 可选：调用该语句清除缓存避免下载到历史旧图
            Call DeleteUrlCacheEntry(sWAN)
            ret = URLDownloadToFile(0&, sWAN, sLAN, BINDF_GETNEWESTVERSION, 0&)
            
            If ret = 0 Then
                .Cells(i, 3) = "File successfully downloaded"
            Else
                .Cells(i, 3) = "Unable to download the file"
            End If
        Next i
    End With
End Sub

注：你当前写的VBA7 64位兼容声明中LongPtr的用法是正确的，只要放对代码位置就不会触发该编译错误。

内容的提问来源于stack exchange，提问作者shampouya