I remember that a very similar question has ben asked in the past, but unfortunately I haven't been able to find the according thread. So, I'm going to start from scratch.
WSUS Offline itself isn't meant to do such a thing, when using its regular function out of the box anyway. However, there are parts in WSUS Offline that can help achieve what you want. Namely it's wsusoffline\client\cmd\ListMissingUpdateIds.vbs which is used to determine missing updates on the clients before installing them. You can also use my HideUpdates script
viewtopic.php?p=20852#p20852 which does something similar. In any case, both scripts contain code that can help writing your own script if you so desire. In case you want to use my HideUpdates but don't understand German, please feel free to ask anything that's unclear (the explanations in HideUpdates.ini and output of HideUpdates.au3 are in German only).
Regards
Dalai