Second attempt. This time with the eval syntax correct. Tried with Bourne Shell, ksh and Posix Shell.
#!/bin/sh
cell1="one"
cell2="two"
cell3="three"
i=1
while [ $i -lt 4 ]
do
var_name="cell${i}"
eval echo \$${var_name}
i=`expr $i + 1`
done
one
two
three