Expression on curve effect property

Hi,

I'd like in my script to add an expression on a curve effect and it seems not supported. Here is a snippet to demonstrate my problem :

alert(app.project.item(1).layer("H01P048_MV_CH_Grp01.[00604-00648].exr").property("Effets" ).property("Courbes").property("Courbes").canSetExpression)

try

{

    app.project.item(1).layer("H01P048_MV_CH_Grp01.[00604-00648].exr").property("Effets").pro perty("Courbes").property("Courbes").expression = "test";

}

catch(e)

{

    alert(e);

}

It always returns False and the following exception :

"Unable to define expression or expressionEnabled for this property."

What seems weird to me, is that manually in After Effects I can add this

expression.

Anyone have any clues?

Thanks in advance