Mitch,
Got it working at VB6 side. (with some help)
Final problem was
0 to255 = 256 values where 0 to 254 = 255 values.
And if you send only 255 and you tell it to expect 256 you have a problem.... 
I am now able this code to be shown in VB6 in the graph.
if (i < switchpointXValue)
lookupTable[i] = map(i, deadbandXvalue, switchpointXValue, speedstartValue, switchpointYValue);
But this curve code is not yet visible.
Have to check if Arduino sends this also in serial monitor first, as I forgot whether it does or not.
else
lookupTable[i] = (int)(0.5 + switchpointYValue + (255-switchpointYValue) * ( 1.0 - pow( (255-x)/(255-switchpointXValue), endCurvePower) ));
Still busy to get the shield working properly and also redesigned the buttons for the MENUWIZ(ard)
So some large rewrite of the program too.
Keep you U all posted.
Paco