Colorbar problems

[francesco.spada(at)jrc.it (Francesco)]

Please could you help me with this colorbar problems?

When I plot the topography I use this lines:

cctop=intarr(20)
cctop(0)=10
cctop(1)=100
FOR i=1,19 DO BEGIN
   cctop(i) = cctop(i-1) + 4
endfor
;
contour,z, POSITION=[0.15, 0.15, 0.95, 0.75],$
  xstyle=9,xtitle='x-axis (km)',ystyle=9,ytitle='y-axis (km)',$

levels=[-.1,.0,25,50,100,200,300,400,500,600,700,800,900,1000,1250,1500,$
   1750,2000,2500,3000], $
  ticklen=-0.02, c_colors=cctop,charsize=1.5,/fill

but I don't know if is possible to set up David colobar in a correct
way
(or if you have a better idea for plotting topography).
The biggest problem is that I plot levels with irregular distance, 
the only idea I have is putting the same "irregularity" in cctop!! 
but I think is more than bad programming :-((

I have a similar problem here

level_var=FLTARR(14)
color_var=FLTARR(N_ELEMENTS(level_topo))
step_col=14
FOR i=0,N_ELEMENTS(level_var)-1 DO BEGIN

level_var(i)=MIN(var2d)+i*(MAX(var2d)*1.1-MIN(var2d))/N_ELEMENTS(level_var)
ENDFOR
;
CONTOUR,var2d,XSTYLE=1,YSTYLE=1,xf,yf,LEVELS=level_var, $
  POSITION=xposition, CHARSIZE=chr_sz, $
  TITLE=title,XTITLE=xtitle,YTITLE=ytitle,/nodata
CONTOUR,var2d,XSTYLE=1,YSTYLE=1,xf,yf,LEVELS=level_var, $
  C_COLORS=color_var, ; could be that without this line it's all right
...
/OVERPLOT,/FILL
CONTOUR,var2d,XSTYLE=1,YSTYLE=1,xf,yf,LEVELS=level_var, $
  /OVERPLOT, COLOR=3,THICK=tck