Interaction between Excel and Word OLE

Question

I am using Office 2007 to write procedures but a problem is apparent only when run on Office 2013.
A procedure in a workbook that records Sales information runs to transfer data to another workbook that stores Invoice information, and then opens Word to generate a mail merge document from a template (dotm) which has an event procedure (on Open) to merge
data from the Invoice spreadsheet into a document to produce an invoice.  This procedure works without problem on the Office 2007 (Vista) machine and until recently likewise ran without problem on the Office 2013 (Windows 8.1) machine.  However,
apparently following an automatic update to the Office 2013 machine, when the Word document is generated the procedure "hangs" at the point of reading the data from the Invoice workbook, and after a longish delay a message is generated along the
lines of the program awaiting an OLE action.  The only way to stop the whole process is via task manager.
After much research I have found that on the Office 2013 machine, the mail merge of data from the Invoice workbook will not now work if the Invoice workbook is open, bot works OK if it is closed.
I have therefore programmatically closed the Invoice workbook, and the procedure now works on the Office 2013 machine (and on the Office 2007 machine).  However, I would like the Invoice workbook to be open when the Word document has been generated. 
I therefore inserted a few seconds wait into the procedure to allow the mail merge to be completed, then tried to reopen the Invoice workbook.  I now get the message that the Invoice workbook is locked for editing, and asking if I want to open a read
only copy (which I don't).  The Invoice workbook does not appear on the task bar, nor does it appear in task manager.  I have tried code to make it active and I then get "subscript out of range", and I have tried code to make it visible
and I again get "subscript out of range".  However, if I close down the word documents generated with the data from the Invoice workbook, I can then open it;  presumably the merge process is treated as still being in progress while the
documents are open, and the Invoice workbook is "released" when the documents are closed.
Has anyone any advice to offer on how to deal with this problem of not being able to open the Invoice workbook while the mail merge documents are open.  The problem is apparent in both Office 2007 and 2013.

Answer 1

Hi Caillen
Thanks for looking at this.  I should explain that I do all my work on an Office 2007 machine for a family member who lives elsewhere, so I don't have direct access to the Office 2013 machine.  However, they are reasonably computer literate and
report faults accurately.  To deal with your queries:
1.  Their Office (and Windows) updates are installed automatically.  Basically, their systems are kept up to date.  It is only a guess that an update may have caused the problem, for the procedure worked as expected for some months and no
other changes have been made.  The problem does not occur on my Office 2007 machine.
2.  For the initial problem there was no error message initially;  the little circle just kept going round for a minute or so, then a message appeared on the Office 2013 machine saying that Excel was waiting for another program to complete an OLE
action.  That message no longer appears because I have cured the problem by closing the workbook that is the data source for the mail merge.
3.  I do indeed mean VBA code by procedure (Sub xxx()).  The code in the Word Template on which the procedure originally hung up was the third line below - i,e, the line starting ActiveDocument.MailMerge.OpenDataSource Name:= _
Sub ctPrintInvoice()
    ActiveDocument.MailMerge.MainDocumentType = wdFormLetters
    ActiveDocument.MailMerge.OpenDataSource Name:= _
        ThisDocument.Path & "\ColTarInvoices.xlsm", _
        LinkToSource:=True, _
        Revert:=False, _
        Format:=wdOpenFormatAuto, Connection:="DETAILS", _
        SQLStatement:="SELECT * FROM `'Print Invoice$'`", SQLStatement1:=""
"DETAILS" is a named range within the workbook that is the data source for the mail merge.  "Print Invoice" is the name of the worksheet that holds the data.  This code runs as an event on opening the document, which is done
automatically within the code in the workbook.  The code in the Sales workbook to open the document is:
    Set objWord = CreateObject("Word.Application")
    If strSourceSheet = "Sales" Then
        Set objctMergeDoc = objWord.Documents.Add(ThisWorkbook.Path & "\ctInvoice1.dotm")
    ElseIf strSourceSheet = "Euro Sales" Then
        Set objctMergeDoc = objWord.Documents.Add(ThisWorkbook.Path & "\ctEuroInvoice1.dotm")
    End If
    objWord.Visible = True
    Set objWord = Nothing
    Set objctMergeDoc = Nothing
However, the procedure also hung in the same place on the Office 2013 machine if the document was opened manually.
4.  The code in the Sales workbook to close the Invoice workbook is:
   Workbooks("ColTarInvoices.xlsm").Close
The code to reopen it is:
   Workbooks.Open (ThisWorkbook.Path & "\ColtarInvoices.xlsm")
This generates the message that the workbook is locked for editing.  The same message is generated if I try to open the workbook manually while the merged documents are still open.
(The files are all in the same folder)
With thanks
Andy C