[TYPO3-templavoila] How do I get the value of an input field into typo script

[Henrik Bøgelund]

I am creating a new data structure in TemplaVoila, and have run into a 
seemingly simple problem.
I have created an element called field_menu with Element Preset = Link 
field.
This gives me a field in the page properties where I can select a page, 
and when i do so, the page id is shown in the field.
So far everything is good.

My intention is to create a menu with all the subpages of the selected page.
Therefore I have entered this in the 'TypoScript Code' field of field_menu:

10 = HMENU
10 {
   special = directory
   special.value = 32
   wrap = |
   1 = TMENU
   1 {
     noBlur = 1
     expAll = 1

     NO {
       wrapItemAndSub = <li>|</li>
       ATagParams = class="menu-links"
       ATagTitle.field = description // title
       beforeImgLink = 1
     }

     ACT < .NO
     ACT = 1

     ACT {
       wrapItemAndSub = <li class="current_page_item">|</li>
       beforeROImg <
     }
   }
}

This actually works, in the sense that it creates a menu of all subpages 
of page-id 32.

And here comes my question:
How do I replace the fixed value (32) with the page id of the page I 
select in the page property?