Graph Initial and Final Value

I have a groundwater graph of date versus elevation.  The date (X-axis) and elevation (Y-axis) are either default based on the data it is pulling or I have user report variables available for setting the min/max of date and elevation axes.   I have used the DTGraphInitValue and DTGraphFinalValue fields to show the min and max dates at either end of the X-axis.  There does not seem to be similar available functions that I can find in Help for the minimum and maximum values on the Y-axis.  I guess I could search for max and min on the elevation data and round, but I'm wondering if there is an easier way.   I want to be able to show depth on the other Y-axis.  Any shortcuts?