Please make relations part of the tab order. Once the relations field has the "focus" .. an "enter" should be the same as a "click" event.
OR.. provide the ability to populate a choice with the results of a select. I was lazy.. and imported all the States .. full name .. abbreviations.. etc... into a table.. and associated it to my Address table.. :(
Pushing values to choice fields is something we are having on the radar.