Shell Programming and Scripting

Hi all,
I am rather new to shell programing
I am trying to run a loop through variables that already exist,
here is (a part of ) the code, variables param_kz etc already exist (in the same file, i do not run another script file etc) and have values assigned to them (strings, "y" or "n")

Code:

echo $param_kz
#counting the number of perturbations
paramnr=0
for pw in kx ky kz kB kCs
do
echo param_$pw
echo $[param_${pw}]
if [ $[param_${pw}] == "y" ] ; then paramnr=`expr $paramnr + 1`
fi
done
echo $paramnr
echo $param_kz

the echo $param_kz before the loop and after it is just to check if the (already existing) variable is what i set it to earlier in the code.
Seems in the loop it treats the param_${pw} as new variables, since echo $[param_${pw}] returns zeros (even though they are either "y" or "n").
The funny thing is that a similar construction works for a friend on his laptop. So, my question is, is there a way to do this the way i am trying, am i missing something, does the older version of bash somehow creates new variables in loops in this sense, or what ? I tried

Code:

for pw in "kx" "ky" "kz" "kB" "kCs"

, to no avail
Sure i can do it some other way, but it is annoying when you do not know why a seemingly good idea doesn't want to work ...
Thanks
Luk

Here's an example to put you on the right direction:

Code:

param_kx="y"
param_ky="n"

paramnr=0

for pw in kx ky
do
  eval "var=\$param_${pw}"
  echo $var
  if [ "$var" = "y" ] then
    paramnr=$(( paramnr + 1 ))
  fi
done