Change the order of the post

I have made a custom template for a wordpress page. This template lists all posts in a certain category.
I want to change the order of the post, so they are listed ascending by a custom field named date. The date in the custom field is formatted like this: "d/m/Y". I also want to exclude posts where the date has passed.

For the order of the post basen on a custom field use
meta_key=CustomFieldName&orderby=meta_value In your query.

Thanks for the response.
How do I use this in my query?
When I replace <?php query_posts('category_name=events'); ?> on line 29 with <?php query_posts('meta_key=Dato&orderby=meta_value'); ?>, i break the code.

Thanks in advance.