Restricting preview text to the text that is entered in that field

Is there a way to restrict the preview text to the preview text that is entered, rather than that text plus the text from the Email body?

I came across this hack last year and it worked back then -not sure if still works. It does require you to hand code your email though.

Thanks! I have used this before in my own code, but can you add code to the structure of the templates in Infusionsoft?