'先声明函数

Private Declare Function CopyFile Lib "kernel32" Alias "CopyFileA" (ByVal lpExistingFileName As String,ByVal lpNewFileName As String,ByVal bFailIfExists As Long) As Long

'D:\1.txt复制到C:\2.txt-----0表示文件存在时就覆盖

rst = CopyFile("D:\1.txt","C:\2.txt",0)

If rst = 0 Then MsgBox "替换不成功！" Else MsgBox "替换成功！" End If