Define a macro to produce title, author, ...

Hello everyone! I have a series of reports to write, which have similar titles,  e.g.
title:My Title   subtitle:1   author:me   date:today
title:My Title   subtitle:2   author:me   date:today
title:My Title   subtitle:3   author:me   date:today

So I wrote a macro for this:
```
<assign|title|
  <macro| order |
     <doc-data| <doc-title| My Title>
                      | <doc-subtitle| \order>
                      | <doc-author| me>>>>
```
In preamble.
(The "\order" is entered by \order[enter] in texmacs)
(The <doc-data.... Part is copied from a manually inserted title)

But when I call this macro, it displays a literal "order" as subtitle, and I can't change it.

I want to know what's wrong with this macro, and how to fix it?
(I'm new to TeXmacs and is still learning, so please forgive me if this question is stupid.)