Here is my take.
Assuming you have macro B on the machine.
The following is a hacked up version of the code I have used to make an ellipse.
Basicly just replaced the Y value with the A at the current angle.
Back plot in NCPlot is just a line but when animated you can see it speeding up and slowing down as it should.
The step angle can be made as small as needed for the finish but very small values will slow down the machine.
Code:
(CHANGE AS NEEDED)
(CHANGE AS NEEDED)
#100= 2 (RADIUS)
#101= 1.0 (Y SCALE, 1.0 FOR A CIRCLE)
(OTHER VALUES MAKE AN ELLIPSE)
#102= 1 (STEP ANGLE)
(----------------------)
#103= 0 (CURRENT ANGLE)
G1X[#100*COS[0]]Y[#101*#100*SIN[0]]
WHILE [#103 LT 360] DO1
(USE THE FOLLOWING LINE TO DO A CIRLE IN X,Y PLANE)
(G1X[#100*COS[#103]]Y[#101*#100*SIN[#103]]F10.0)
(OR)
(USE THE FOLLOWING LINE TO DO THE SIMPLE HARMONIC MOTION)
G1X[#100*COS[#103]] A[#103]F10.0
#103=#103+#102
END1
(G1X[#100*COS[360]]Y[#101*#100*SIN[360]])
G1X[#100*COS[#103]] A[#103]F10.0
G0X0.0Y0.0