Is paying building management to run discrete cable an option? Either they, or you, purchase the materials and have fiber run between the two suites in the common areas that are controlled by building management. Fiber between the suites is fairly secure (difficult to intercept) and resistant to interference. Fiber gives you much greater distance limits than does copper, and bandwidth all the way to 10GE without any changes to the fiber. You have to have an ethernet switch with fiber uplink on each end of the fiber to convert back to copper to connect to the desktops. The switch on each end could be as simple as a Netgear GS510TP, all the way to enterprise Cisco class hardware.