如何在installshield中的软件之前检查并安装另一个软件requeriment？

I'm doing a software that requires from OpenVPN to work, so I'm expecting that when I launch the installer checks if OpenVPN is installed and if not launch it's installer. If the install is successfull then continue with the install, if not, exits. Also, I'd like to check if O.S is 32 or 64bits in order to launch the correct installer from openvpn.I'm doing a software that requires from OpenVPN