Growing / Shrinking Window

I’m looking to build a “popup” window that will grow in height to a certain point when a button is clicked. When another “close” button within this window is clicked, it will shrink back down to its original height. I also want to be able to load text in a dynamic text field within it, using a sendandload.

Are there any good tutorials for this sort of thing? I am having quite the time figuring out the best way to go about this.