This Scrippy creates a never ending top and side border, with a corner graphic covering the seams where the two border scrolls meet.  It's simply created by inserting a top border scroll and a left border scroll using the graphics below.

Then a transparent corner graphic, as shown below, is added and positioned at zero pixels from the top and zero pixels from the left to cover the seams created from the top and side scrolls.   You could also add a small container in place of this corner graphic and fill it with whatever you like to cover the seams.

The Message Area and the border will automatically expand to fit any amount of text entered.