[Anonymous]

The "Required When" behavior can be achieved without coding a custom action.  In QWP 5.4.1, you can create a form component behavior that will check the value of one field (e.g., check if the field is null) and make another field required.  For example, the form component xml behavior below is placed on the "Contact Type" field.  If the Status field is equal to behind, then the Contact Type field can not be null which makes the field required.  When Contact Type is null and the user clicks the Save button, then the user sees the message,"Contact Type is required when Status is Behind".

<FormComponentBehavior>

  <Component Type="Field" ID="Contact Type">

    <RequiredWhen Message="Contact Type is required when Status is Behind">

      <Eq>

        <FieldRef Name="Status" />

        <Value Type="Text">Behind</Value>

      </Eq>

    </RequiredWhen>

  </Component>

</FormComponentBehavior>

Curtis