How To Detect Where Text Wraps

What I'm trying to do is insert hard-coded line breaks where ever the text wraps inside a div or td element (or any other element, I suppose). The point is to ensure that the text always wraps in the same place in print as it does on screen, which in turn will ensure that the container element is always the same height in print as it is on screen. It needs to work on non-monospaced type, so counting characters isn't really an option.

I've done lots of googling on this and the only thing I've found that even acknowledges that wrapped text has multiple lines is the getClientRect() method. This method returns a collection of rectangles-- one for each line of text in the container element. This can be used to determine how many lines there are, and the dimensions of each, but I don't think that really helps me, unfortunately.