Task fields in the required property

[adam_bo_]

In a task I have two fields and I want to set the required property to true in field_YYYYYY when field_XXXXX is true. How can this task's field be binded from EL? Here is an example:

  <widget name="field_XXXXXX" type="checkbox">
    <labels>
      <label mode="any">field_XXXXXX</label>
    </labels>
    <fields>
      <field>['field_XXXXXX']</field>
    </fields>
  </widget>

  <widget name="field_YYYYYY" type="htmltext">
    <labels>
      <label mode="any">field_YYYYYY</label>
    </labels>
    <fields>
      <field>['field_YYYYYY']</field>
    </fields>
    <properties widgetMode="edit">
      <property name="required">#{??????????}</property>
    </properties>
  </widget>

All the best