I'm trying to write a batch file to find and replace an IP address in the hosts file. 

I did a bit of research and found this, but it doesn't seem to work. I get the final echo of "Done." but it doesn't work. 

```
@echo off

REM Set a variable for the Windows hosts file location
set hostpath=%systemroot%\system32\drivers\etc
set hostfile=hosts

REM Make the hosts file writable
attrib -r %hostpath%\%hostfile%

setlocal enabledelayedexpansion
set string=%hostpath%\%hostfile%

REM set the string you wish to find
set find=OLD IP

REM set the string you wish to replace with
set replace=NEW IP
call set string=%%string:!find!=!replace!%%
echo %string%

REM Make the hosts file un-writable
attrib +r %hostpath%\%hostfile%

echo Done.

```