Cannot reference one sketch to another

I am fairly new to Creo so bear with me.  Say I sketch a spline on one datum plane and then start a sketch on a perpendicular datum plane.  I want the spline that I sketch on the second perpendicular datum to be coincident with the point on the first spline that insects the second datum that I am currently sketching on.  I cannot figure out how to do this.  I tried using the Reference button to make the first spline a reference for my second sketch but it doesn't seem to work.  I can never get the cursor to snap to a point on the first spline.  Any suggestions?