Phil,
The code I have placed below came from some kind soul posted on this
UseNet. When the Workbook_Open procedure runs upon opening the file--we
will call the child document--this code will look to see if the file
name you supply is open--lets call it the parent document. If the
parent document is open it will exit the Workbook_Open procedure.

1. Paste the line of code mentioned below in your Workbook_Open
procedure located in the code for 'ThisWorkbook'; change the file name.

2. Next Paste the TestWorkbookOpen function below the end of the
Workbook_Open procedure.


Public Sub Workbook_Open()
Application.ScreenUpdating = False

'1. Place this line of code in your workbook_open procedure...
If TestWorkbookOpen("TheParentFileName.xls") Then Exit Sub

'Your code here...
Application.ScreenUpdating = True
End Sub

' 2. Next Paste the TestWorkbookOpen function below the end of the
Workbook_Open procedure.
Function TestWorkbookOpen(WorkBookName As String) As Boolean
' returns TRUE if the workbook is open
TestWorkbookOpen = False

On Error GoTo WorkBookNotOpen
If Len(Application.Workbooks(WorkBookName).Name) 0 Then
TestWorkbookOpen = True
Exit Function
End If

WorkBookNotOpen:
End Function