Код:

@echo off
setlocal enableextensions enabledelayedexpansion
set sString=bla-bla-bla add bla-bla-bla
if "%sString%" neq "%sString:add=%" (
echo Yes
) else (
echo No
)
set sString2=bla-bla-bla ad bla-bla-bla
if "%sString2%" neq "%sString2:add=%" (
echo Yes
) else (
echo No
)
endlocal
exit /b 0