Vertical profile

[David Muhati <muhati@xxxxxxxxxxxxxxxxx>]

Hi ferret users,
My model output is a 4-D field i.e
 name     title                                            I         J 
    K         L
 QM1      specific humidity 
(qm1)          1:128     1:64      1:19      1:3811

I want to plot a vertical profile (with z as the coordinate axis) of the 
variable QM1 above
along a longitude,say 30E. I tried looking at an example in the archives 
but couldn't get
on well. I welcome suggestions on this.
Thanks alot!!