A while ago I explained the work flow I’m using often in that case, only for the last field you need to have either a shortcut or a submit button AND the sequence has to be imposed. The idea is that you make the Submit button for the first field transparent, delete the ‘Submit’ text and put it over the second field. So if the user clicks on the second field, he also submits the value of the first field.
Here is the blog post I’m referring to:
Although it was written for previous versions, the idea will still be functional.