TWordApplication and Word collision - delphi

Question

I am using TWordApplication in Delphi. My app opens new instance of word and make something on its document. Problem is when i first run my app and next open real word exe. Word exe didnt open new word instance but it link to my app instance. So when my app write to its document all text appears on exe word visible to user.
WordApp := TWordApplication.Create(nil);
WordApp.ConnectKind := ckNewInstance;
(WordApp.Documents.Add(EmptyParam,EmptyParam,EmptyParam, varFalse ));
Then the user opens Word manually.
WordApp.Selection.Text := 'test test test';
And user see 'test test test' in manually opened Word.
If i first opens Word manually and starts my app all is ok.

Answer 1

This is default behaviour of Word, it uses a running instance. What you have to do is store a reference to the document you want to modify. So don't use ActiveDocument, but use the Document you stored. Because there is no guarantee that ActiveDocument is the document you think it is.
//starting Word
var
App: TWordApplication;
Doc: WordDocument;
begin
App := TWordApplication.Create(nil);
Doc := App.Documents.AddOld(EmptyVar, EmptyVar); //open new document
<..somewhere else..>
//modifying Word
Doc.DoWhateverIWant; // <--see? no ActiveDocument, so you are not
// modifying the users doc

Answer 2

Make sure you use
WordApp.ConnectKind := ckNewInstance;
to open your word application. Either do it in code (as above) or set the property at design time. This ensures that you are always running a new instance of Word and that it remains hidden unless you explicitely make it visible. Any user opening Word will then always get a different instance of Word and will not see what you have put on the document (unless you have saved it and they open the saved document).
From the doc:
Set ConnectKind to indicate how the
ConnectKind component establishes a
connection. ConnectKind establishes
the connection when the application is
run (if AutoConnect is True true) or
when the application calls the Connect
(or ConnectTo) method.
The following table lists the possible values:
//Value Meaning
//ckRunningOrNew Attach to a running server or create a new instance of the server.
//ckNewInstance Always create a new instance of the server.
//ckRunningInstance Only attach to a running instance of the server.
//ckRemote Bind to a remote instance of the server. When using this option,
// you must supply a value for RemoteMachineName.
//ckAttachToInterface Don't bind to the server. Instead, the application supplies an
// interface using the ConnectTo method, which is introduced in
// descendant classes. This option can't be used with the AutoConnect
// property.
Update
Actually, opening Word may have opened a different instance (that's how I remember it for D5/Word97), but at the moment Word does indeed re-use the instance opened by the application. So to avoid "scratching all over a word document manually opened by a user" you really do need to avoid using ActiveDocument as per The_Fox's answer.

Answer 3

According to http://support.microsoft.com/kb/210565 there are several command line switches that will cause Word to start a new instance. The one I have used with Word2003 is /x