Change coordinates x and y for the three points in the Custom Functions/Constants list. Let the constant x0 "run" from zero to one to draw curve. Change the argument range to show more or less of the graph. For the graph to be drawn as x0 "runs" set the argument range from 0 to x0.
The first grf is a Beziercurve Drawer using 6 controlpoints.
The second grf is a Beziercurve Drawer using 3 controllpoints.
The bottom grf is a Beziercurve Drawer using 4 controllpoints.
Have fun (: