Modules & VBA :: Making Already Opened Excel File Invisible

I have the following code. In the Else part of the code, after the wb.Activate line, what code can I place here that will assign wb.Name to the objExcelApp object ao that when the line .Visible = False kicks in, it will make the already opened MS Excel file invisible.

Code:
Dim strExcelFile As String
Dim wb As Workbook
Set objExcelApp = GetObject(, "Excel.Application")
If objExcelApp Is Nothing Then
Set objExcelApp = CreateObject("Excel.Application")
objExcelApp.Workbooks.Open FileName:=strExcelFile

[code]...