Configure this property to define whether this Tag must be automatically written when the Value property or any Bit property (from Bit00 to Bit31) is modified. If this property is set to True, changes are sent to the device or equipment linked to the OPC Driver, otherwise these changes are ignored. If this property is set to True, then the Driver automatically updates Value and Bit (from Bit00 to Bit31) properties of this object, in time spans. Otherwise, this OPC Block is not read. Default value of this property is True. Example:

Sub Button1_Click()
  Set obj = Application.GetObject("Driver1.tag")
  obj.AllowWrite = False
End Sub