Block All Uploads but Allow Downloads

We are using Intercept X on all of our workstations and I would like to setup a policy where users cannot upload files to any sites.  (webmail, online storage, etc.)  But I want them to be able to still download from those same sources.  Is this possible?  I don't care about the content of the files.

I tried using a DLP policy, but it seems to be an all or none type thing.

Thanks.