Files Delphi

Title: How can I know an application file whether it is in use or not?
Question: is an application in use?
Answer:
Within a program, you may want to know an application file whether it is in
use or not.Then you can use the following function.
Function ApplicationUse(fName : string ) : boolean;
var
HFileRes : HFILE;
begin
Result := false;
if not FileExists(fName) then exit;
HFileRes := CreateFile(pchar(fName), GENERIC_READ or GENERIC_WRITE,0, nil,
OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL, 0);
Result := (HFileRes = INVALID_HANDLE_VALUE);
if not Result then CloseHandle(HFileRes);
end;
This is an example of using this function:
procedure TForm1.Button1Click(Sender: TObject);
begin
if ApplicationUse('c:\project1.exe') then
ShowMessage('Application in use')
else
ShowMessage('Application not in use');
end;