Overflow error while opening 2nd Excel - vba

Question

I am looking for help after many hours of research.
My problem is a little bit tricky but...
I am working on new Excel-VBA Applications for my company.
I developped some code to help me to open new instances of Excel everytime I open a new workbook.
My problem comes when i try to open a second Excel while my workbook is already open. I get an un-understandable error 6 Overflow.
There are the tools that I developped to open new Excel instances.
Option Explicit
Private WithEvents ThisExcelApplication As Application
Private WithEvents OtherExcelApplication As Application
Private l_blnSaveNewWorkbook As Boolean
'Procédure : Workbook_Open
'Event : opening workbook
Public Sub Workbook_Open()
Debug.Print Time & " : ThisWorkbook\Workbook_Open()"
If Application.Workbooks.Count > 1 Then
Call ReOpenApplicationInNewExcelInstance
Else
l_blnSaveNewWorkbook = False
End If
Set ThisExcelApplication = Application
Load ufConnection
ufConnection.Show
End Sub
There is my Workbook_open, it checks if there is an existing workbooks opened then it opens my workbook on a new excel instance. But my problem doesn't come from here.
Private Sub ThisExcelApplication_WorkbookOpen(ByVal Wb As Workbook)
Dim strFile As String
If Wb.FullName = ThisWorkbook.FullName Then Exit Sub
Set OtherExcelApplication = CreateObject("Excel.Application")
strFichier = Wb.FullName
Wb.Close False
If g_blnApplicationVisibility Then
ThisExcelApplication.Visible = True
Else
ThisExcelApplication.Visible = False
End If
OtherExcelApplication.Visible = True
OtherExcelApplication.Workbooks.Open strFile
End Sub
Private Sub ReOpenApplicationInNewExcelInstance()
Dim oExcel As Excel.Application
Dim strFiler As String
Dim strTemporaryFileName As String
l_blnSaveNewWorkbook = True
Set oExcel = CreateObject("Excel.Application")
strFile = ThisWorkbook.FullName
strTemporaryFileName = ThisWorkbook.Path & Application.PathSeparator
& "TemporaryFileName.xlsb"
'save current workbook on a temporary file to free the access of original workbook
Application.DisplayAlerts = False
Application.EnableEvents = False
ThisWorkbook.SaveAs strTemporaryFileName
Application.EnableEvents = True
Application.DisplayAlerts = True
'close the original workbook and re-open it on new instance
oExcel.Workbooks.Open strFile
'close the 1rst workbook and kill the temporary files
ThisWorkbook.ChangeFileAccess xlReadOnly
Kill strTemporaryFileName
ThisWorkbook.Close False
End Sub
When I open a second workbook when the 1rst one is already open, the ThisExcelApplication_WorkbookOpen Method is logicaly called. It checks the name of the opened workbooks. If it is not the same name, it tries to open a new excel instance and open this workbook on it.
Then i get the error 6 Overflow on this line :
OtherExcelApplication.Workbooks.Open strFichier
Maybe someone have an idea to help me?
Thanks a lot for your attention.
PS: Sorry for my english, it might be bad !