more specific query based on custom field date

so here is my query

<?php query_posts('cat=shows&order=desc&orderby=meta_value&meta_key=show_info_date&showposts=4'); ?>

which works great. orders the events by my magic field custom date etc… but i only want it to show events that are – lets say – in the coming week… does anyone have any leads on that ??? thanks.