If you're not to be dissuaded, at some other part of your app, include this:
window.checkIsIE = navigator.userAgent.indexOf('MSIE') != -1;
You can now refer to "checkIsIE" as a Boolean variable that indicates whether the user is using IE.
Unclean and lazy? Yes; so is the fundamentals of what you're doing. In all honesty, I can't deny that even my own work has resulted in problems that can't be solved in the clean way, but please be reminded that the clean way is to check whether the browser in question supports the features you need from it. There are even frameworks that can help you determine if certain CSS features are supported (Modernizr comes to mind).
The above code does not detect IE 11 - and I consider that a plus, since a good solid bet says that whatever strange, old-IE bug you're trying to circumvent does not occur in IE11.