Is it possible to set up a custom field that requires a specific format eg xx-xxxx-xxxxxxx-xxx
I'd suggest adding a javascript formatter to a single, custom input text field. I haven't tried it, but formatter.js looks like it would deliver what you want.

Their Credit Card demo illustrates what you want - accepts pasting of data with and without hyphens, prevents pasting / input of values which don't match the validation rule. It just needs a different pattern for hyphen placement to deliver bank accounts.