Change recycling of an application pool

I currently have a recycle time for an application pool.  I need to change it.  According to the MS documentation (https://technet.microsoft.com/en-us/library/cc754494(v=ws.10).aspx) The format should follow:

appcmd set apppool /apppool.name: Marketing  /recycling.periodicRestart.schedule.[value='15:00:00'].value:17:00:00

However, when I follow that format, I get: "ERROR ( message:Cannot find requested collection element. )"

Can someone suggest?

Thanks,

OJ King