Hi Paco,
It looks like the dimension declaration is wrong for the graph.
The Variant business just complicates things.
There is very little about line graphs in VB.
I found this slightly lower level code:
You have to scale the 0-255 coordinates to be graph values (use map) before drawing them.
You have only 3 pairs of XY data:
0, 0
switchPointX, switchPointY
255, 255
After that you could add drawing the hor speedstart line and vertical deadband lines (dotted).
You could also add some of the lookuptable points between the switchpoint and (255, 255) to see the curve.
Sorry I haven't done Visual Basic.