Anatoliy,

Based on your request: "I want an instantiated object to be able to retrieve hwindow value and not able to modify it".

I've modified your class a little bit as follows:

o = NEWOBJECT('myclass',"myclass.prg")
o._hwindow = 8  && An error will result "Property _hWindow is not found" -- "not able to modify it"
?o.GethWindow() && this retrieves the _hwindow property value -- "be able to retrieve hwindow value"

DEFINE CLASS myclass As Custom
HIDDEN _hwindow
_hwindow=0  
PROCEDURE Init
	THIS.SetHWindow

PROTECTED PROCEDURE SetHWindow
	DECLARE INTEGER GetFocus IN user32
	THIS._hwindow=GetFocus()

FUNCTION GetHWindow
	RETURN THIS._hwindow
ENDDEFINE

Hope this helps.