PHP with Javascript

Hi there everyone, I have a problem, I am populating my first dropdown box on my form from my MySQL DB with PHP no problem, but when I select the item it has to refresh the whole page to put the items into the second dropdown box, is there an EASY :-) way of populating the second box with Javascript so that the page doesn't have to refresh? I'm a total Jscript newbie, but I figured that Jscript is what I need to use with PHP and MySQL to achieve this? I know this is somewhat about Jscript but it's also about PHP and MySQL :-) I just need to find the best way to populate the second box without having to refresh the whole, page so any ideas/examples would be very welcome :-) Thanks for everything. Chris