excel-vba 打开一个（新的）工作簿，即使它已经打开
示例
如果要访问已经打开的工作簿，则从Workbooks集合中获取任务很简单：
dim myWB as Workbook
Set myWB = Workbooks("UsuallyFullPathnameOfWorkbook.xlsx")如果要创建新的工作簿，请使用Workbooks集合对象Add创建新的条目。
Dim myNewWB as Workbook Set myNewWB = Workbooks.Add
有时您可能不会或（或不在乎）您所需的工作簿是否已打开，或者可能不存在。示例函数展示了如何始终返回有效的工作簿对象。
Option Explicit
Function GetWorkbook(ByVal wbFilename As String) As Workbook
'--- returns a workbook object for the given filename, including checks
' for when the workbook is already open, exists but not open, or
' does not yet exist (and must be created)
' *** wbFilename must be a fully specified pathname
Dim folderFile As String
Dim returnedWB As Workbook
'--- check if the file exists in the directory location
folderFile = File(wbFilename)
If folderFile = "" Then
'--- the workbook doesn't exist, so create it
Dim pos1 As Integer
Dim fileExt As String
Dim fileFormatNum As Long
'--- in order to save the workbook correctly, we need to infer which workbook
' type the user intended from the file extension
pos1 = InStrRev(sFullName, ".", , vbTextCompare)
fileExt = Right(sFullName, Len(sFullName) - pos1)
Select Case fileExt
Case "xlsx"
fileFormatNum = 51
Case "xlsm"
fileFormatNum = 52
Case "xls"
fileFormatNum = 56
Case "xlsb"
fileFormatNum = 50
Case Else
Err.RaisevbObjectError + 1000, "GetWorkbook function", _
"The file type you've requested (file extension) is not recognized. " & _
"Please use a known extension: xlsx, xlsm, xls, or xlsb."
End Select
Set returnedWB = Workbooks.Add
Application.DisplayAlerts= False
returnedWB.SaveAsfilename:=wbFilename, FileFormat:=fileFormatNum
Application.DisplayAlerts= True
Set GetWorkbook = returnedWB
Else
'--- the workbook exists in the directory, so check to see if
' it's already open or not
On Error Resume Next
Set returnedWB = Workbooks(sFile)
If returnedWB Is Nothing Then
Set returnedWB = Workbooks.Open(sFullName)
End If
End If
End Function