You could create another field called monitor assigned 2, and only populate it if the computer has a second monitor.
There might be a better way of doing this, if there is, I'm sure someone will post it here.
I would think you would have the same problem in Access as you have in Filemaker and the solution can even be the same in both systems.
I'd consider setting up a relationship based on a Workstation ID number.
You might have a workstation with the following data in a table:
WID SerialNo. Description
1 54326 CPU
1 45672 15" Monitor
1 67231 17" Monitor
1 34561 Keyboard
and so forth.
The WID value of 1 in the above example tells you that all of the above equipment are part of the same workstation. You can set up one table for Workstations to generate your WID values and relate it to your equipment table to list all the various components.
At the risk of being obvious
There is a white paper for FMP novices at
I have found it useful.
Few people know that (on WIN and MAC) you can have multiple keyboards and mice plugged in and active at once.....
Since you are familiar with MS Access, you might find a post in this thread: Re: Setting up a relational database with existing tables helpful, as it compares the two DBs in an effort to help identify features in FMP that are roughly equivalent to what you find in MS Access.