Currently the sketches are not defined and the splines don't fully intersect each other. The portion(s) of the splines that do not intersect are the portions that are missing from the curve. There needs to be some simple relations for them. The end points of sketch24 should be horizontal to the appropriate endpoints of sketch23. This should do it or most of it. If the very ends of the curve are a bit funky, play with the handles on the splines a bit. To make this more visual friendly, you could extrude each sketch so that they intersect each other. Select both surfaces, choose the Intersection Curve tool, and the resulting 3Dsketch is the Curve.