I forgot to mention; for a quick test (experiment), I put all the code in Form.Init(). Of course, you will have to decide eventually when you want to execute the code, for example, in a Button.KeyPress(), or with a Timer.

Here is another example, with a Timer, which will draw the sine curve slowly.

Create form properties .x = 0, .y = 0, .i = 0, and place the following code into the Timer.Timer Event:

with ThisForm
	.i = .i + 0.05
	.x = .i*100
	.y = sin(.i)*100 + 100
	.Line(.x, .y)
	if .i >= 2*pi()
		This.Enabled = .F.
	endif
endwith

I know, it is not perfect; this is just a quick sample. I'll leave the details to you.