Search Box to search another blog/site..

Hi!

I have 3 websites. A, B and C.

What i’m trying to achieve is have C contain search boxes that search A and B. if you search on the search box for site A you’d be directed to a new page showing the results of that website. same with site B.

I hope it makes sense. I think it’s just a small modification to my current search form but I don’t know what to edit to achieve this result.

Here is my search box code:

<form method="get" id="search-plus" class="searchbox alignright" action="<?php bloginfo('home'); ?>" >
		<input id="search-box-plus" type="text"  name="s"  value=" Enter keywords.. " onfocus="this.value=(this.value==' Enter keywords.. ') ? '' : this.value;" onblur="this.value=(this.value=='') ? ' Enter keywords.. ' : this.value;"/>
		<input type="submit"  value="Search!" id="searchbutton-plus"/>
	</form>

Thank you in advance!