sounds like you have your BE path wrong. As for adding it to your server.bat just add "start dayzbec.bat" before the executable.
@echo off
color 0a
title Server Starter
:top
echo Executing pMain()
.\MySQL\bin\mysql --user=root --password=root --host=127.0.0.1 --port=3316 --database=hivemind --execute="call pMain()"
ping 127.0.0.1 -n 5 >NUL
echo Complete!
ping 127.0.0.1 -n 1 >NUL
cls
echo Launching And Watching Server
start /wait .\Expansion\beta\arma2oaserver.exe -mod=@dayz;@hive -name=cfgdayz -config=cfgdayz\server.cfg -cfg=cfgdayz\arma2.cfg -profiles=cfgdayz -world=Chernarus -exThreads=0 -maxMem=1024
ping 127.0.0.1 -n 5 >NUL
echo Server has exited ... Restarting!
ping 127.0.0.1 -n 1 >NUL
cls
goto top
@echo off
echo Starting MySQL database. Please wait 5-10 seconds.
start /MIN /D.\MySQL\ MySQL.bat
ping 127.0.0.1 -n 15 >NUL
.\MySQL\cecho {0A}OK.{07}
echo.
echo.
echo.
echo Executing spawn script...
.\MySQL\bin\mysql --user=root --password=root --host=127.0.0.1 --port=3316 --database=hivemind --execute="call pMain()"
ping 127.0.0.1 -n 5 >NUL
.\MySQL\cecho {0A}OK.{07}
echo.
echo.
echo.
echo Starting server...
start /REALTIME .\Expansion\beta\arma2oaserver.exe -mod=@hive;@dayz -name=cfgdayz -config=cfgdayz\server.cfg -cfg=cfgdayz\arma2.cfg -profiles=cfgdayz -world=Chernarus -cpuCount=4 -exThreads=1 -maxmem=2047 -noCB -noSound
.\MySQL\cecho {0A}OK.{07}
echo.
echo.
echo.
echo.
echo.
echo.
.\MySQL\cecho {0B}Launcher created by Pwnoz0r.{07}
ping 127.0.0.1 -n 5 >NUL
echo.
echo.
echo.
echo.
.\MySQL\cecho {0A}Leaving le launcher...{07}
ping 127.0.0.1 -n 5 >NUL
echo.
echo.
echo.
echo.
echo.
exit