To specify an axis range you must change the axis view to range axis view - for exampe:
NChart chart = nChartControl1.Charts;
chart.Axis(StandardAxis.PrimaryY).View = new NRangeAxisView(new NRange1DD(0, 100), true, true);
will limit the Y axis to show values in the range 0 - 100. Is this the functionality you're looking for? - or maybe you want to allow the user to also use scrolling / panning - if this is the case just let us know and we'll post code to accomplish this.
Let us know if you have any questions or meet any problems.
Nevron Support Team