ExcelVBA中提示错误9,下标越界,怎样解决?

Sub 拆分到工作簿()

Dim wk As Workbook, ss$, k%, sht As Worksheet

Application.DisplayAlerts = False

For Each sht In Workbooks("2-11.工作簿综合运用(拆分工作簿)").Sheets

    Set wk = Workbooks.Add

    k = k + 1

    Workbooks(1).Sheets(k).Copy Workbooks(2).Sheets(1)

    ss = ThisWorkbook.Path & "\" & sht.Name & ".xlsx"

    wk.SaveAs ss

    wk.Close

Next

Application.DisplayAlerts = True

MsgBox "拆分工作簿完成！"

End Sub

在For Each 这一行中出现“运行时错误9  下标越界”