Fighting a Losing Battle

I'm losing the Grass Wars battle. Don't get me wrong. I love grass, especially in the spring and fall when growth spurts turn the grass into a wondrous neon green. But I don't like grass growing in my gravel driveway. Twice every year I get out my pump sprayer and attack the grass growing in the driveway. I use Round-up and spray the driveway thoroughly, using a stronger-than-called-for mixture of Round-up and water. It's supposed to kill grass for a year. It doesn't. In 6 months I have to spray again.

I don't want to mow my driveway. I like the clean, crisp look of a manicured lawn and weed-free driveway. But no matter how often I spray my driveway, the grass keeps coming back. I wish I knew a cure for driveway grass! I've tried everything: boiling water, vinegar, hot oil (note to self: do not dump donut-frying oil in your driveway--it will attract every varmint for miles around!). Nothing seems to work. If you have any tips for getting rid of grass permanently, do let me know!