if statement problem

I keep getting an error at line 21, it doesn't like my if statement. Previously I have tried using (( )), but still get errors. The current error is that server_busy is not found. This is the script:

#! /bin/ksh
server_busy="na"
for file in $1 $2 $3 $4 $5 $6
do
 echo " ${file}\t\c"
 /eagle/progress/dlc/bin/proutil ${file} -C holder > /dev/null
 ret=$?
 case $ret in
    0) server_busy=""
       echo me
       echo "Not Active";;
   14) echo "Locked";;
   16) echo "Active in Multi-user mode";;
    *) echo "Recv'd Error [${ret}]";;
 esac
done
read dummy
echo ${server_busy}
~
~
~
~
~
:q
[mrc:/eagle/aix/scripts]vi startscript
#! /bin/ksh
DBPARAM="-spin 1 -bibufs 100 -n 35 -B 500 -L 64000 -directio -Mm 4096"
PDIR="/eagle/aix/params"
for i in `find /eagle/aix -name "APPSERVERS" -depth -print`
do
  appserver_list=`cat -v ${i}`
done
server_busy="na"
for file in $1 $2 $3 $4 $5 $6
do
 echo " ${file}\t\c"
 /eagle/progress/dlc/bin/proutil ${file} -C holder > /dev/null
 ret=$?
 case $ret in
    0) server_busy=""
       echo "Not Active";;
   14) echo "Locked";;
   16) echo "Active in Multi-user mode";;
    *) echo "Recv'd Error [${ret}]";;
 esac
 if ${server_busy} = "";
   then
   echo "Proserve ${file} -basename ${file}"
   if -f "${PDIR}/basename ${file}.pf" ]; then
    echo "Using parameter file ${PDIR}/basename ${file}.pf"
    /eagle/progress/dlc/bin/proserve ${file} -S basename ${file} -pf ${PDIR}/basename ${file}
   else
    /eagle/progress/dlc/bin/proserve ${file} -S basename ${file} -pf ${DBPARAM}
   fi
   /eagle/progress/dlc/bin/probiw ${file}
   /eagle/progress/dlc/bin/proapw ${file}
   /eagle/progress/dlc/bin/prowdog ${file}
 fi
done
   sleep 1
   for appsrvr in ${appserver_list}
   do
     /eagle/progress/dlc/bin/asbman -name ${appsrvr} -start
   done

added code tags --oombera

Try changing it to:

if [ $server_busy = "" ];
then
...
fi