You can use a Property Node to write an array of 11 values to the XScale.MarkerValues[] and YScale.MarkerValues[] arrays. You'll have to calculate the grid line locations from your actual data; in your example, I just picked my own sets of grid lines which mostly fit the sample data (see attachment).
Sometimes, the graph doesn't update right away. There are various tricks to force an update. In this example, I've chosen the crude but effective technique of hiding and showing the graph.
