How to get Inno Setup to check for a file

When I compile the Inno Setup script below, it gives me an error (below). I borrowed the code here , so I'm not sure why it is not working properly.

Line 136:
Column 10:
Invalid prototype for 'FileDoesNotExist'

Line 136 is function FileDoesNotExist(file: string): Boolean;

[Run]
Filename: "{sys}\regsvr32.exe"; Parameters: "msstdfmt.dll"; WorkingDir: {app}\Pronto\Programs\; BeforeInstall: FileDoesNotExist(ExpandConstant('{sys}\msstdfmt.dll')); StatusMsg: "Registering Controls..."

[Code]
function FileDoesNotExist(file: string): Boolean;
begin
  if (FileExists(file)) then
    begin
      Result := False;
    end
  else
    begin
      Result := True;
    end;
end;