Only allow to open files from specific directory

Hello,

we use Acrobat and Reader as part of creative cloud in our company. In one department we view .pdfs with linked .docm/.doc/.xlsm/.xlsx/.pdf - files, in all others we only have .pdf to .pdf links. To prevent maleware to spread through attached files, we disabled opening non-.pdf-files and only allowed it in the mentioned department and activated sandbox / protected mode.

As this is an severe security problem and our company was targeted by a virus using this leak, I would like to limit this. Best case would be allowing only word and excel to be opened and only files from the directory the mentioned department works in.

- I tried to set up a whitelist ("ProtectedModeWhitelistConfig.txt"), which only led to unexplainable behavior (links to other directories than the ones listed in the whitelist would work rather than the allowed ones; powerpoint would open, excel would not).

- I tried to make the directory (on a server) a trusted "internet" source, as recommended in a discussion in this forum by an adobe employee, which would not work

- I tried to make the directory a trusted source in the extended settings, which would not work either

Can anyone relate or help?

I really need this to be solved in order to close this security leak and I think there are others with the same / a similar  problem.

Thank you!