Heres the multi-key code, maybe you can do something with it.
Mob/Owner
verb
Multi_Key_Check()
set category = "Staff"
set desc = "Check all Player for Multi-Keying"
var/Found[0]
for(var/mob/M in world)
if(Found.Find(M))continue
if(M.client)
for(var/mob/M2 in world)
if(!M2.client)continue
if(!M2)continue
if(M == M2)continue
if(M.client.address == M2.client.address)
Found += M
Found += M2
usr << "<B>\red Match Found!"
usr << "<B><font color = #999999>Name:</font> [M.name] <B><font color = #999999>- Key:</font> [M.key] <B><font color = #999999>- Address:</font> [M.client.address]."
usr << "<B><font color = #999999>Name:</font> [M2.name] <B><font color = #999999>- Key:</font> [M2.key] <B><font color = #999999>- Address:</font> [M2.client.address]."
Example: