Load the script then go to Commands -> Check Prices, enter the name of the RuneScape item and click check, the top 5 results will be shown in the text box below.
www.runescape.com
Update - 30/07/07
I've fixed the price checker, also it now returns more results for your search and has an option to message the selected result to the active channel.
Random-Mate, to use this script, you must have mIRC installed. To get mIRC you can visit http://www.mirc.com/ once mIRC is installed copy the above script and in mIRC press alt+r. Paste it in there and then in a channel window right click in the background and click on what you want.