I use custom fields in sheetset Manager every single day in AutoCAD 2013. I did however have an installation problem where I could not format my formula fields which caused me to have to delete my entire profile off of my computer and start over from scratch (even the autodesk clean install instructions didn't help; I uninstalled, repair installed, and reinstalled, literally 9 times). Can you upload a screenshot of the exact problem area you are talking about? I originally installed from my subscription download, and it caused my profile to get corrupted for some reason.
(P.S. I also use product design suite)