Well then ask how to do it from the command line also
Take a look at Xnest, you'll have to read the man page to
see if it can pull remote desktop.
You can also pull individual "apps" from remote desk like this:
From you user login on Box A:
$ xhost+
ssh uselogin@remotebox
$ export DISPLAY=BoxA.somehting.net or use ip address
Now run what ever app you want to display:
(Box A)$ netscape &
And it should pop up on your local desktop