Add a modal window with a gravity form that can by dynamically populated based on the current post.
<?php if ($status != 'sold') : ?>
<a href="#" class="mgButton" data-toggle="modal" data-target="#featModal">Book A Viewing</a>
<?php endif ?>
<div class="modal fade" id="featModal">
<div class="modal-dialog">
<div class="modal-content">
<div class="modal-header">
<button type="button" class="close" data-dismiss="modal"><span aria-hidden="true">×</span><span class="sr-only">Close</span></button>
<h4 class="modal-title"> Request About <?php the_title(); ?> </h4>
</div>
<div class="modal-body">
<?php $property = get_the_title(); ?>
// property is a parameter name set in the gravity field form options
<?php gravity_form(1, false, false, false, array('property' => $property), true); ?>
</div>
</div><!-- /.modal-content -->
</div><!-- /.modal-dialog -->
</div><!-- /.modal -->