find and replace using sed

Hello Everybody,
I am doing something like this on Redhat Linux

h=`cut -d"." -f4 file1`
s=`cut -d"." -f4 file2`
sed "s/$h/$s/g" file3

but this is not working
but if giving constant value its working,
for ex. sed "s/93/$h/g" file3
help...
Thanks for looking into my question

Try enclosing variable with single quotes, e. g. sed "s/'$h'/'$s'/g" or 's/'$h'/'$s'/g'. This works in unix, but it may depend on the values of your variable.

getting something like this in Debugg "set -x"
used your suggestion
sed "s/'$s'/'$h'/g" filename
o/p ++ sed 's/'\''93 '\''/'\''101 '\''/g'

earlier getting something as
o/p ++ sed 's/93 /101 /g'
when using this: sed "s/$s/$h/g" filename

problem not resolved