Schedule A VM Export

I'm running Vcenter 5.5 and my hosts range from 5.1 to 5.5.  Does anyone know a way I can automate the export of a virtual machine?  I would like to have a VM saved to an ova or ovf file on a UNC path daily overwriting the old file.  The virtual machine is very small only a few gigabytes.  Does anyone know of free software or a script that can accomplish this? 

Thanks,

Dave