The basic issue is that the XY graph is a graph, not a chart. No matter what you do to the axis values, the graph just plots pairs of XY coordinates. You will need to manipulate the gata going to the graph so that it appears to update like a chart does.
Keep the data is a shift register and manipulate it as needed before plotting. Say for the example you only want to plot the last 100 points, buffer the data in the shift register as it comes in being careful to only save the last 100 points, then plot whatever is in the shift register.
Do a little searching. There have been numerous examples posted over the years.
Mike...
