conditional markup change with AjaxEditableLabel

[fhagen]

Hi, 

i am using a subclass of AjaxEditableLabel.
This one works fine so far but I have one Problem.

If the value of the label is < 0 the markup should change.
I tried it this way with no effect.

public class MyAjaxEditableLabel extends AjaxEditableLabel{

protected void onSubmit(AjaxRequestTarget target)
{
        [...]
        if(position.getValue()[index] < 0)
        {
                this.getLabel().add(new AttributeModifier("class", true, 
new Model("negativ")));
        }
        else{
                this.getLabel().add(new AttributeModifier("class", true, 
new Model("positiv")));
        }

        this.getLabel().setVisible(true);
        this.getEditor().setVisible(false);
        target.addComponent(MyAjaxEditableLabel.this);
}

}

In my css - stylesheet the class "negativ" and "positv" are defined.
So if the value of the label changes to < 0 nothing happens.

Any suggestions?

Fabian