Is it possible to input data into a field and have Filemaker automatic return or tab to next field?

Yes, it sounds like you want a script trigger.

How would Filemaker know you have finished inputting?

I have a feeling this is the same issue as here:

http://fmforums.com/forum/showtopic.php?tid/217669

That was going to be my next question.

Is it a fixed number of characters or digits, like an area code?

yes it would be a fixed number of two letters and 4 numbers at the end. It is a scanned barcode number. I need it to go to the next field after the code is input into a field.

Any ideas?

Thanks Much

Most scanners can append a character to the end of the scan, such as enter, return or tab, thus taking you to the next field. No script required, you just have to configure the scanner, and select the corresponding field behavior options.