如何将默认文档分配给变量

Question

背景

使用从Excel运行的VBA来抓取/打开AutoCAD并开始绘制新的绘图。

到目前为止我有什么

到目前为止，我所尝试的内容取自我在网络的各个部分找到的内容：

Sub Open_AutoCad(NewFile As AcadDocument, ACAD As AcadApplication)

'Dim MyAcadPath As String
'Dim bReadOnly As Boolean


    On Error Resume Next
    Set ACAD = GetObject(, "autocad.Application")
    If (Err <> 0) Then
        Err.Clear
        Set ACAD = CreateObject("autocad.Application")
        If (Err <> 0) Then
            MsgBox "Could Not Load AutoCAD!", vbExclamation
            End
        End If
'*****************************************
    Set NewFile = ACAD.Documents.active  <-need correct syntax for active document
'*****************************************
    Else
        Set NewFile = ACAD.Documents.Add
    End If

    ACAD.Visible = True



'    PREVIOUS OPEN METHOD THAT IS HARD CODED FILE PATH       
'    MyAcadPath = "c:\Temp\Blank Drawing.dwg"
'    bReadOnly = True
'    Set NewFile = ACAD.Documents.Open(MyAcadPath, bReadOnly)
'
'    If (NewFile Is Nothing) Then
'ErrorMessage:
'        If NewFile = "False" Then End
'            MsgBox "Could not find the required file that should be located at" & vbCr & MyAcadPath & vbCr & "Please rename or relocated the specified file as needed."
'        End
'    End If



    'close AutoCAD Process
    'ACAD.Quit

    'Set ACAD = Nothing
    'Set NewFile = Nothing

End Sub

我最初是从硬编码路径打开一个绘图，但这不是我想要发生的。我想要获取恰好在autocad中设置的默认模板文件并使用它。以为它可以节省必须确保所有用户都拥有硬编码路径。

问题

我选择使用ACAD.Documents.Add方法添加默认模板文件，效果很好。问题是AutoCAD在打开特定文件时（至少在我的系统上）自动创建Drawing1。因此，当我点击.Add时，我会结束Drawing2，并且所有工作都将在drawing2中执行。所以为了避免这种情况，我只使用.Add方法，如果AutoCAD已经存在/正在运行。这方面工作正常。当AutoCAD作为其打开例程的一部分创建时，如何将Drawing1分配给变量Newfile？

根据Chris的建议更新了代码：

Sub Open_AutoCad(NewFile As AcadDocument, ACAD As AcadApplication)

'Dim MyAcadPath As String
'Dim bReadOnly As Boolean


    On Error Resume Next
    Set ACAD = GetObject(, "autocad.Application")
    On Error Goto 0
    If ACAD=Nothing Then
        Err.Clear
        Set ACAD = CreateObject("autocad.Application")
        If (Err <> 0) Then
            MsgBox "Could Not Load AutoCAD!", vbExclamation
            Exit Sub
        End If
'*****************************************
    Set NewFile = ACAD.Documents.activedocument
'*****************************************
    Else
        Set NewFile = ACAD.Documents.Add
    End If

    ACAD.Visible = True

End Sub