The property is used only if the graphic mode is set.
On setting it can be set the value in pixels or the value can be set in percentage of the whole viewer length. For example oTrendArea.Dx = "84%".
On reading from the property is always returned the value in pixels.
var oTView = pMe.Items("../TrendView");
var oTrendArea = oTView.TrendArea;
var nDx = oTrendArea.Dx;