Add-in that adds code to new Excel Workbooks - vba

Question

I'm trying to change my add-in so that it, when you would open a new Workbook, will open a new Sheet and then create a new Event Procedure in that new Sheet.
I've gotten to the point where I can "Sheets.Add" and ".CreateEventProc" using a macro button combination, but the issue comes when trying to use the add-in's Workbook to automate the process. The add-in loads in first, thus "Set VBProj = ActiveWorkbook.VBProject" can't find the new active workbook.
Is it possible to do this? If so, is there a work around needed or am I just missing something obvious?
Here's what I have at the moment:
Option Explicit
Private WithEvents App As Excel.Application
Private Sub Workbook_Open()
Set App = Excel.Application
End Sub
Private Sub App_NewWorkbook(ByVal Wb As Workbook)
Range("T2").Value = 100
ActiveWorkbook.Sheets.Add
Call CreateEventProcedure
End Sub
Public Sub CreateEventProcedure()
Dim VBProj As VBIDE.VBProject
Dim VBComp As VBIDE.VBComponent
Dim CodeMod As VBIDE.CodeModule
Dim NumLines As Long
Dim LineNum As Long
Dim ProcName As String
Dim ProcKind As VBIDE.vbext_ProcKind
Const DQUOTE = """" ' one " character
Set VBProj = ActiveWorkbook.VBProject
Set VBComp = VBProj.VBComponents("Sheet2")
Set CodeMod = VBComp.CodeModule
With CodeMod
LineNum = .CountOfDeclarationLines + 1
Do Until LineNum >= .CountOfLines Or ProcName = "Worksheet_Change"
ProcName = .ProcOfLine(LineNum, ProcKind)
LineNum = .ProcStartLine(ProcName, ProcKind) + _
.ProcCountLines(ProcName, ProcKind) + 1
Loop
If ProcName = "Worksheet_Change"
GoTo Exi
End If
'Now, create a Change Event on Sheet2
LineNum = .CreateEventProc("Change", "Worksheet")

Answer 1

For those who care, I got the process working with a minor complication. Here's what I did:
Option Explicit
Private WithEvents ExApp As Excel.Application
Public Sub ExApp_WorkbookOpen(ByVal Wb As Workbook)
Dim StrPrompt As String
Dim strTitle As String
Dim iRet As Integer
StrPrompt = "Want to create event?"
strTitle = "Event?"
On Error GoTo 0
iRet = MsgBox(StrPrompt, vbYesNo, strTitle)
If iRet = vbYes Then
ActiveWorkbook.Sheets.Add
Call CreateEventProcedure
End If
On Error GoTo 0
ActiveWorkbook.Sheets.Add
Call CreateEventProcedure
End If
End Sub
Private Sub Workbook_Open()
Set ExApp = Excel.Application
End Sub
I created the Yes/No prompt to Bypass the first 'run-time _Global' error and then the excel workbook actually loads, the prompt asks me again then I click yes and everything works fine. Also, this works with only one prompt needed when opening workbooks when already in excel.