The value entered here is used as initialization value for trend viewer (for the PmgTrendViewer object). The value is entered in the following property: tvTrend.ValueMax
nMax = pMe.Pm("/data/#vars/Temperature/#ext/trend").Max;
//or
nMax = pMe.Pm("/data/#vars/Temperature").Extension("trend").Max;
//or
nMax = pMe.Pm("/data").Item("Temperature").Extension("trend").Max;