how to draw a image with color bar on real page (draw color bar on parea)

[z z]

hi all
1. I want to draw a color bar with cbarn.gs. But this color bar seems
have to be draw on a vpage. I need a image without title, axix lale
etc.
The part of the script file likes:

'open test.ctl'
'set lon -67 -56'
'set lat 40 50'
'set t 1'
....
'set vpage 0 11 0 8.5'
*'set parea 0 11 0 8.5'
'set xlab off'
'set ylab off'
'set gcout shaded'
'd z'
'printim result.png x800 y600 white'
'run cbarn 1 0 5.5 0.8'
'quit'

if i used "set vpage  ' the color bar will be drawed on the bottom of
the visual image. while it did not work on the parea.

Any suggestion?

2 Is there any way to define the output interval of a variable?
For example, there is a temprature variable defined in the control
file. The output may range from 10 degree to 20 degree (11 lines with
1 degree interval) for a particular coordinate ((-67, -56) (42 48)) If
I cahnge the narrow the coordinate to ((-65,-60) (43 46)), I still
want there are 11 lines displayed on the image (may 0.3 degree
interval).How can I do this?

Thanks a lot