>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
When I make my own class, for ex:
DEFINE CLASS cstBox AS custom
x1 = 0
y1 = 0
x2 = 0
y2 = 0
FUNCTION draw
< draw a box with x1,y1,x2,y2>
ENDFUNC
ENDDEF

if I want to change the size of that Box, first i'm changing the properties and call DRAW() method.
Can VFP do that, after I changes the property values withoout calling DRAW() method
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

If you are using VFP 6.0, check out the _assign methods. They're pretty well documented in the Help file, but basically, the Assign fires when you change a value. So, you can attach an Assign method to each of the properties, and call your Draw() function. This will redraw after each property change, though, which might not (or might) be the desired behavior.

In VFP 5.0 you could rework your logic a little -- pass the four value to the draw method as parameters, for instance [i.e., This.Draw(15,21,14,22)].