I use CS and the resize only affects one dimension with no way, but one (which I'll describe), to change the other dimension. What I do is just make one click to get the size that I want then hit Edit - Transform - Scale and change the percentages at the top of the screen.
This is also heavily dependent upon what kind of border that you are playing with...sometimes resizing will make it connect poorly. Say your using a vine for your border and you resize it...the vert border and the horiz border will look very different. On the other hand, if you are using egg and dart then it should look okay.
The best thing to do is do one thing for the corners and something else that fits in between them and can be repeated easily (the smaller the chunk the better it will repeat). If you post up an image I'll take a look at it and see if we have to go and chop it up