How to disable header button of a collapsible in jquery mobile?

How to disable header button of a collapsible in jquery mobile?

I have a simple collapsible, made with jquery mobile. How can i disable
the button in the header of the collapsible which is meant to expand
collapse the collapsible? I want to disable it, being still able to
collapse/expand programmatically. The whole thing is meant to prevent the
user to collapse/expand in order to have the complete programmatical
control of the moment a collapsible has to be expanded or not.
<div data-role="collapsible" data-collapsed="true" id="d27" name="d27"
class="ui-block-a">
<h4></h4>
<div class="ui-block-a">
<legend>D27: Dopo il test, ti sei poi iscritto ad Economia alla
Sapienza?</legend>
</div>
<div class="ui-block-b">
<fieldset data-role="controlgroup" data-type="horizontal">
<input type="radio" name="iscrittoEconomia" id="si27" value="1" />
<label for="si27">Sì</label>
<input type="radio" name="iscrittoEconomia" id="no27" value="0"
checked="checked" />
<label for="no27">No</label>
</fieldset>
</div>
</div>
This is the button i mean: