OLE Application Excel Intercept (and deal with) Window messages

Using OleApplication in Delphi to use Excel.

Have to append data as it appears, to existing sheets if they exist, without operator intervention.  

For new workbook all is fine, but if the workbook is already there, Excel generates a windows message which the Delphi program should deal with - such as 'This file already exists - Do you want to save?'  appears.  

How would you trap these messages to make an automated system?
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mornaoAsked:
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SuperUtConnect With a Mentor Commented:
I have solved a similar problem as follows:
I create a helper thread that performs the desired action on the COM object that might pop up a window.
While that's going on, I look for a pop-up dialog and I let my program press the OK button to close the dialog.

Here is the code that I got to work after some trial and error:

Parameter s is the caption of the pop up window I look for,
TOms is the max. time I wait for the pop up to appear since the pop up window doesn't always show up.

procedure PressOKButton(Sender: TObject; s: AnsiString; TOms: integer);
var
   h1, h2: thandle;
   tag: tagInput;
   TimeOut: TDateTime;
begin
   //Enum windows and press OK button
   TimeOut:= now + TOms/ MSecsPerDay;
   Repeat
      h1:= FindWindowEx( 0, 0, Nil, pAnsiChar( s));
      if h1 = 0 then
         sleep( 50);
   until ( h1 <> 0) OR( now > TimeOut);

   if h1 <> 0 then begin
      h2:= FindWindowEx( h1, 0, Nil, 'OK' );

      if h2 <> 0 then begin
         SetActiveWindow ( h1);
         Windows.SetFocus( h1);
         Windows.SetFocus( h2);  //OK button
sleep(20);
         tag.Itype:= INPUT_KEYBOARD;
         tag.ki.wVk:= 0;
         SendInput( 1, tag, sizeof( tag));
sleep(20);
         SendMessage( h2, BM_CLICK, 0, 0);
sleep(20);
      end;
   end;
end;





Here is a sample of the main thread

procedure BO_Refresh;
begin
   FHelperThread:= Nil;
   try
         FHelperThread:= tHelperThread.Create( True );
         FHelperThread.FreeOnTerminate:= False;
         FHelperThread.Resume;
         PressOKButton( Nil, 'Select Values', 20000);

         FHelperThread.WaitFor;
   finally
      FHelperThread.Free;
   end;
end;



This is the only code of the helper thread:
//------------ Helper thread
procedure tHelperThread.Execute;
begin
   BusObjDoc.Refresh;
   Terminate;
end;
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TomGrillsCommented:
try setting the DisplayAlerts property to FALSE

    XLApplication.DisplayAlerts:=false;
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mornaoAuthor Commented:
While that turns off all mesages, would like to trap then and decide based on what the message says.
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mornaoAuthor Commented:
Still no answer to this one - and as a result had serious Americanisation issues.
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