module.php

<?php

function module_ClientArea(array $params) {

	// Get the template file, the $_REQUEST can be set in your default template to change sections
	$Template_Area = isset($_REQUEST['template_area']) ? $_REQUEST['template_area'] : '';

	// Select the templates files depending on the requested area
	if ($Template_Area == 'cool_place') {
		$Template_File = 'templates/cool_place.tpl';
	} else {
		$Template_File = 'templates/overview.tpl';
	}

    // Return the template file to be used when loading the client area. 
    return array('tabOverviewReplacementTemplate' => $Template_File);
}

template.tpl

<form method="post" action="clientarea.php?action=productdetails">
  <input type="hidden" name="id" value="{$serviceid}" />
  <input type="hidden" name="template_area" value="cool_place" />
  <button class="btn btn-default">
  	{$LANG.module.Go_To_Cool_Place_Button}
  </button>
</form>