AutoCAD Inventor :: Macro Failed When PDF File Is Already Open

I created a macro for generate a PDF drawing, but when one file has been already created, AND he's already open, the macro don't work.

How to stop the macro automatically and notify that the macro has been stopped because the file is open.

Below, the current macro :
 
Sub PublishPDF()'Get the PDF translator Add-In.Dim PDFAddin As TranslatorAddInSet PDFAddin = ThisApplication.ApplicationAddIns.ItemById("{0AC6FD96-2F4D-42CE-8BE0-8AEA580399E4}")'Set a reference to the active document (the document to be published).Dim oDocument As DocumentSet oDocument = ThisApplication.ActiveDocumentDim oContext As TranslationContextSet oContext = ThisApplication.TransientObjects.CreateTranslationContextoContext.Type = kFileBrowseIOMechanism
[Code] ....