Question about @AVE

[Ming Yang <myang@xxxxxxxxxxxxx>]

Hi, folks
    I have a Netcdf dateset like this:
 name     title                             I         J         K        L
 T2M      Temperature at 2 Meter           1:64      1:32      ...     1:12000


The I coordinate represents longtitude. I would like to use @AVE transfromation
to compute the average value of the variable T2M over several grids, but
the problem is the grids I would like average include the 0
longitude, So that in the @AVE transfromation I have to include I=60:64
as well as I=1:5. I am wondering what is the easiest way to do this
calculation in ferret? Thank you in advance.

Best,
Ming