Hello Bestpaperboy -
If you have a listing showing on the Scheduled listings page of your account all you need do is go to the Scheduled Listings page - from the listings menu - and select the checkbox next to the listing you wish to prevent from posting and click on the Cancel Posting button near the top of the page. Alternately, you can locate the item on the same page and click the Cancel button on the extreme right side of the entry which has a red circle with slash icon on it. This will cancel the scheduled posting.
- Craig