// add conditional logic for the GForm notification message
add_filter('gform_pre_submission_filter_1', 'conditional_message');
function conditional_message($form){

// define field IDs for conditional logic
        $choice1 = RGForms::post('input_49.1');
        $choice2 = RGForms::post('input_48.1');

        // append a different html text for payment options
	if($choice1)
		$form['autoResponder']['message'] .= "Message 1";
	if($choice2)
		$form['autoResponder']['message'] .= "Message 2";

        // return modified form
        return $form;
}