Hi VBAhack, this information is great but unfortunately I am having trouble creating a VBA spline function. I have found some examples online, some which allow me to specify end point conditions such as natural or a specific value for slope or curvature, however I want to use parabolic and cubic runouts for the endpoints but cannot find out how to code this. Do you happen to have a VBA function where you can specify end point conditions which include these? In these cases the curvature is not simply a hardcoded value but is dependent upon the curvature of the portions of the spline next to the end points, so I am unsure how to code this. Any help would be greatly appreciated!