How to disable one separate effect control?

Hi. I put my own effect to PresetEffects.xml

    <Effect matchname="ADBE Dynamic Transition control" name="Dynamic Transition control">

    <Slider name="Duration" default="2" valid_min="0" valid_max="20"/>

    <Slider name="Begin Value" default="0" valid_min="-5000" valid_max="5000"/>

          <Slider name="End Value" default="0" valid_min="-5000" valid_max="5000"/>

</Effect>

In scripts i add this effect to both layers in composition, which are involved in the "transition" process.

Slider "Duration" of course was created to adjust the duration of the transition.

I need to make that slider "duration" on the bottom layer, was not available to change the value. Because duration of transition depends on expression of the slider on the top layer.

This is certainly not a critical issue. But it is very interesting to know how it can be done. In case if it is required in the future.

Many thanks for any help!!!