What version of FileMaker do you have?
Do you have access to technical info on how to configure your specific scanner?
If you search this forum under "barcode", you should find several threads that discuss setting up a bar code scanner to trip script triggers that then perform scripts that:
a) put the cursor in the correct field to receive the scanned data
b) process the data once scanned to do whatever is needed for the particular barcode system that was set up.