Hotkey to Flip Selected Text as if CAPLOCK had been Toggled when it was Typed

How many times have you seen caps in a text message?
Most of this these cases are because people don't notice but sometimes its because people can't be bothered re-typing the message correctly.
Can we get a Hotkey bind that will allow us to select a block of text and flip the typed characters as if CAPLOCK was toggled when they were typed?  
For example:  “i WAS GOING TO PLAY THAT, TOO!”

Would flip to : “I was going to play that, too!”

Note the punctuation.

The toggle would have no affect on punctuation and numbers but affects the letters typed only.

This would give the people that use CAPLOCK as a hotkey in games, the ability to correct themselves quickly and conveniently.