Why awk does not work in FvwmScript?

I use line below in script to calculate cpu usage:

Set $sp = (GetOutput {echo $(grep 'cpu0' /proc/stat | awk '{usage=($2+$4)*100/($2+$4+$5)} END {print int(usage*118/100)}')} 1 -1)

In console it works well and returns integer number but in FvwmScript does not. What I make wrong?
Thanks in advance.

Nobody can help me? I found solution

ChangeSize 3  (GetOutput {echo $(bash $[HOME]/.fvwm/scripts/StaTux/cpu1.sh)} 1 -1) 2

with script

{ cat /proc/stat; sleep "$DELAY"; cat /proc/stat; } | awk '/^cpu0 / {usr=$2-usr; sys=$4-sys; idle=$5-idle; iow=$6-iow} END {total=usr+sys+idle+iow; print int((total-idle)*118/total)}'

But what is strange - dynamic bar works 5 minutes and then disappears from panel. I thought that the reason is the ChangeSize require integer number and made above. Now the number for ChangeSize is integer but nevertheless it works 5 minutes or less. Any ideas?