Action points incrementer

[Gomo]

Hello.
I'm new here so I apologise if I post in wrong place and wrong way.

I am trying to implement Action point into my system.
Right now I've managed to set it up in similar way to power points (except it is calculated differently).
But I want to go one step further and make it faster to acces and modify by making an similar incrementer that ws used for Initiatibe in tactic form.
I copied the code from Initiative but I stuck at point when I want to access action points field.
I've got such a massage:

Hero Lab was forced to stop compilation after the following errors were detected:

Portal 'totalacts' - Reference to incompatible field type/style/behavior based on portal type

The Field which I specify is copy of health field used elsewhere in incrementer
(dmgDamage)and lies within Actor component. Here is code for it:

<field
      id="acActNow"
      name="Current Actions"
      type="derived">
      <calculate phase="Traits" priority="5100" name="Calc acHPNow">
        <after name="Calc acHPMax"/><![CDATA[
        ~@value = field[acHPMax].value - hero.usagepool[DmgNet].value
		@value = 5
        ]]></calculate>
      </field>

So what I am missing / doing wrong?
Is it some limitation to access derived fields by incrementer?
I should mention that I am not a programmer I merely get some low level script experience.

[Mathias]

Derived fields are intended to only be controlled by scripts.

If you want to let the user control the value of that field with an incrementer, it needs to have type="user", and cannot have a calculate script.

[Gomo]

Thanks, It works.