MultiBlock: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/MultiBlock - from package: vtk-examples

You may install the required package with command yum install {package}

Error in other languages:
MultiBlock: bevel nie gevind nie
MultiBlock: comandă negăsită
MultiBlock: comando não encontrado
MultiBlock: commande introuvable
MultiBlock: command not found
MultiBlock: käsku ei ole
MultiBlock: không tìm thấy lệnh
MultiBlock: komanda nerasta
MultiBlock: Kommando nicht gefunden.
MultiBlock: kommandot finns inte
MultiBlock: komut yok
MultiBlock: nie znaleziono polecenia
MultiBlock: níor aimsíodh an t-ordú
MultiBlock: no se encontró la orden
MultiBlock: no s'ha trobat l'ordre
MultiBlock: opdracht niet gevonden
MultiBlock: parancs nem található
MultiBlock: perintah tidak ditemukan
MultiBlock: príkaz nenájdený
MultiBlock: příkaz nenalezen
MultiBlock: команда не найдена
MultiBlock: командата не е открита
MultiBlock: 命令找不到
MultiBlock: コマンドが見つかりません