changing a magritte description dynamically

> Hi,
> I have a form that's using generated via Magritte descriptions. I'd like to
> be able to change the label on one of the fields dynamically. I thought I'd
> found the solution by overriding #description on the instance-side and
> editing the field's description as in:
> description
> | description pricePerUnitDescription |
> self halt.
> description := super description.
> pricePerUnitDescription := description detect: [:each| each accessor
> readSelector == #pricePerUnit].
> self addCurrencyToDescriptionLabel: pricePerUnitDescription.
> ^ description
> However it seems that the description is cached so this method is rarely
> called.
> Any thoughts on how to dynamically change the label in a magritte field
> greatly received.