if you know font-size, font-style and line-height and I think you know it if it is your site :). You can write javascript function that will add characters to div until it's height is less or equal then two lines height.
Here is sample that worked in all browsers for one line check.
To tell the truth it is not my solution, however my coworker allowed to post it :).
function fitInWidth(name) {
this.empty().append(name);
while (this.height() > 19) {
name = name.substring(0, name.length - 3);
while (name.charAt(name.length - 1) == ' ') name = name.substring(0, name.length - 2);
this.empty().append(name = name + '…');
}
return name;
}