MS Access: Deleting extranious field on text export

I export files from Access as fixed-format text. Sometimes my fingers get ahead of my brain, and I type in the length and starting position of a field that doesn’t exist. Of course I get an error. But there doesn’t seem to be any way of deleting the extraneous field (I’ve tried right-clicking, and I’ve tried deleting the values), and I have to cancel and type everything in again.

Is there a way to delete an extraneous field when exporting?