Anatoliy,

Any object created from the same parent class as the one where check is performed will pass your check.

>So far I decided on creating the InternalCall method in the base class:
>

>* InternalCall
>RETURN (AT(UPPER(THIS.class)+".", PROGRAM(PROGRAM(-1)-2))=1)
>

>to be called from _ASSIGN methods as follows:
>

>* myproperty_ASSIGN
>LPARAMETERS vNewVal
>IF THIS.InternalCall()
>    THIS.myproperty = m.vNewVal
>ELSE
>    ERROR 1533
>ELSE
>ENDIF
>

>So basically it's an extention of your idea of distinguishing between external and internall attempts to change the value of a property.