The best way to restrict access to one file

Holla!

I kinda understand the fact that you cant set file permissions on files like you can within Windows, but.... We have 1 file which we only want a certain amount of users to check out. Its currently within a folder which has a workflow assigned to it, if I move that file outside of the folder I can then assign the rights independantly. The problem is its 4 users within 4 different user groups. Can I just create another group and add them to this group and give that group the rights to check this file out? Leaving them in thier original groups so they can also do whats necessary within PDM and other workflows etc?

Complicated - confused..... Yes I am       

SolidworksSolidworks Pdm enterprise Pdm