A little CSS/JS Help Please

I've been playing around with JQuery for a couple of weeks now. One of the features I love is the datepicker that can easily be added to any text box. One of the things that I've been trying to figure out is how to create a pop up dialog similar to the way the calendar pop up works.

I'd like to have a text box or table cell that has some text in it. In addition I've got an image or button somewhere else on the page. When I click on that element, a small form pop-up shows up under the text box. Now I know that I can do this, but simply putting the form inside a span/div tag, but I want the pop-up to actually pop-up and not affect the layout of the page when it shows or hides.

I know enough CSS and Javascript that I'm not a novice and if all else fails I'm going to attempt to dig through the jquery calendar js code. I'd rather not though. Any help would be appreciated.