Changing Korean keypresses to English

I have a KO/EN keyboard, and OSX is set up to toggle between these two languages. Sometimes, mistakenly thinking I'm using EN layout, I might type the keys "hello" but the corresponding keypresses in KO give me "ㅗ디ㅣㅐ", which is garble.

Is there a way to:

  • select the line of text I wrote in KO
  • change the characters to EN (based on corresponding keypresses?)
  • paste the EN in place of the KO

It looks like this might be able to be adapted to do what you want: