interactive operation on images

hi all
    i use cvShowImage to show a image, and i want to 
get the cooridnate of the cursor. how can i do it?







Change settings: http://www.yahoogroups.com/mygroups, select
   Get Emails (get all posts)
   Daily Digest (one summary email per day)
   Read on the web (read posts on the web only)Or Unsubscribe by mailing 
OpenCV-unsubscribe@xxxxxxxxxxxxxxx