I use the following to open an additional workbook when I start my Excel session. 

Private Sub Workbook_Open()

    If Dir((ThisWorkbook.Path & "\" & Sheets("Data Entry").Range("C35").Value)) = "" Then
        MsgBox "The full path of """ & ThisWorkbook.Path & "\" & Sheets("Data Entry").Range("C35").Value & """ doesn't exist!!  IG data will NOT be populated!"
        Exit Sub
    End If

    Application.ScreenUpdating = False
    Set wrkMyWorkBook = Workbooks.Open(ThisWorkbook.Path & "\" & Sheets("Data Entry").Range("C35").Value)
    ThisWorkbook.Activate
    Application.ScreenUpdating = True

End Sub
Now I want to close it as well... How could I go about making sure this workbook that gets opened is also closed and of course do the error checking that if it wasn't opened because it didn't exist that there wouldn't be anything to close.... Any help is appreciated.