Need Help - Keystroke only (no text) for text entry field?

Hi Everyone!

Is there a way to have a freeform text entry slide accept only a specific keystroke combination to correctly fulfill the prompt?

Basically, I want to remind software users of ours that they can delete the contents of  a field using Cntrl - Backspace. There is no text entry otherwise, just the combination keystroke that needs to be "tested."

Tried several things on the form side of the freeform slide to no avail. Is there a way for me to do this?

Thanks!

Ashley Green