[gradsusr] area and vertical average

[sim.aberson]

I wish to calculate the area average of a variable that is vertically 
averaged between two levels.  I use the command:

'define aveu=ave(ave(ave(ugrdprs,x=1,x=463),y=1,y=425),lev=925,lev=700)'

This seems to take a huge amount of time (a half hour and counting on my 
mac).  Even without the vertical average, for example,

'd ave(ave(wtmpsfc,x=1,x=463),y=1,y=425)'

takes about 3 minutes.  However, just issuing the command

'define u850=ave(ugrdprs,lev=925,lev=700)'

returns the result in just a moment.

Am I doing this wrong?  Is there a more efficient way that I am overlooking?

Thanks,
Sim Aberson
NOAA/AOML/Hurricane Research Division