If you're looking for a meeting place or a good stop around ½ or halfway between Windsor and Milwaukee, you can try Benton Harbor, MI, which is almost 3 hours west of Windsor, or about 3 hours southeast of Milwaukee.
About ¼ or a fourth of the way, you can stop at Albion, MI. This is about 1½ hours west of Windsor.
About ⅓ or a third of the way, you can stop at Kalamazoo, MI. This is about 2 hours west of Windsor.
About ⅔ or two thirds of the way, you can stop at Gary, IN. This is almost 4 hours west of Windsor, or about 2 hours south of Milwaukee.
About ¾ or three fourths of the way, you can stop at Cicero, IL. This is about 4½ hours west of Windsor, or about 1½ hours south of Milwaukee.
If you drive straight through without stopping at all, the total distance is 388 miles / 624 km. The distances shown above don't include local roads to get into each town, so if you're planning a long road trip, make sure you factor in traffic and road conditions, rest stop breaks, and interesting detours along the way. If you're in a rush, you can do the trip with zero stops, and your total travel time would be around 5 hours, 55 minutes.