I need to export a repeated field into Excel. The export will only pass the first value when 'Excel' is chosen as the file format.

CSV or tab delimited would be ok too as they can be opened in Excel. The repeated field will export, but when opened in Excel, it opens with all values in a single cell.

Is there any way to export a repeated field so that each value in the repeated field has its own cell when the file is opened in Excel?

The general advice about repeating fields is that if you have to ask questions about how to use them, you shouldn't be using them. There are many problems with repeats; this is yet another case in point. It would be better to ditch the repeating fields and use a related table.

Create a new FM file with the same field names as the fields you want to export (matching field types, of course). Import the data into this file and choose "Split Repeating Fields into Separate Records". Then import from that file into Excel.

If you'll need to do this regularly, create another table in the file and use the above technique with it. You could even script the import.