Store first value of a compute in a variable?

Hi,

How can we store the first calculated value of a compute command (in a variable) to use it later in the simulation? (and to uncompute the compute command)
For example for the following variable:

compute Vol_1 1 voronoi/atom
compute Voll_1 1 reduce sum c_Vol_1[1]
variable Vol_1 equal c_Voll_1

I used the following two separately, and get errors for both.

variable Vol_1_0 equal ${Vol_1}

{ERROR: Substitution for illegal variable}

The bottom section of the variable doc page has instructions

on how to save early values in variables for later use.

For nested variables, I suggest you debug your script by printing

intermediate values, one by one, using the print command. They

you should be able to identify which specific variable or command

is causing the issue.

Steve