Use this property to specify the position that an OPC Block Element occupies among the Elements configured in the OPC Block's Size property where it is inserted. This property's accepts values from 0 (zero) to a value less than the value defined in Size. For example, configuring an OPC Block Element's Size property to 20, the maximum valid number for the Index property is 19 and the minimum is 0 (zero). This property can be changed after starting communication. Default value of this property is 0 (zero), but when mapping Elements of an OPC Block, Elipse Power Studio automatically sets the Index property to the specified value. Example:

Sub Element1_OnRead()
  MsgBox Index
End Sub