如何修复“工作表类的复制方法失败”错误？

Question

在编译以下程序时，由于工作表类的复制方法失败1004，导致我出错。

Sub Macro1()    
Dim master As Workbook, awb As Workbook    
Dim s1 As String    
Dim s2 As String    
Dim i As Long, N As Integer    
N = 3    
Set master = ThisWorkbook    
s1 = "C:\Users\Desktop\Test\FTPz.xlsx"     

For i = 1 To N    
    s2 = Replace(s1, "z", CStr(i))    
    Workbooks.Open Filename:=s2    
    Set awb = ActiveWorkbook    
    ActiveSheet.Copy after:=master.Sheets(i)    
Next i      
End Sub    

请任何人帮助解决此问题。