True/False IF statement on two different tables

Let me explain what i'm trying to do and maybe there is an easier way of doing this...

Table: Vulnerability

Vul      System

x2123     xyzlaptop

x5252    xyzlaptop

x1235    abclaptop

x3421    deflaptop

Table: Disabled Systems

System

xyzlaptop

deflaptop

I want my report to only report on systems that have not been already disabled.  Becuase i've already disabled the systems that have a vulnerability. So I thought I could just to a new comlumn if statmenet =IF vulnerability [system] = Disabled Systems [system],"True","False") However i just keep getting an error that what ever in the Disabled systems field can't be found because i'm trying to create the column in the vulnerability table...   Any help is greatly appreicated.