1) And what hardware will you use to scan that bar code? This can be done with a scanner that you connect to a USB port. This can be one that must be connected while scanning or one that you can "roam" a location scanning bar codes that you later down load to the computer. It can also be an iPhone or iPad using the device's camera or there are blue tooth scanners you can use with those devices to scan bar codes.
So this is possible, but you need to consider what equipment best fits your needs.
2) USB scanners typically function in "Keyboard Emulation Mode". This means that the bar code is automatically input into the computer just as though you typed the equivalent text from a keyboard. So to scan a bar code into FileMaker with such a device you need only put the cursor into a field and then scan a bar code.
iOS devices using FM GO would use their integral cameras to scan a bar code using the Insert From Device script step. I believe that most blue tooth scanners will emulate a blue tooth keyboard, but I have not used such hardware so I could be wrong.
If using a USB scanner, you may find this thread to be of interest: Need help writing script to integrate barcode scanning