>I have two pc's One of the with VFP5, the other with VFP6. I made the change with VF6, (couldn´t find addproperty in VF5), the continue the change in VFP5, but the propperty disappared.. What happened

Well, VFP5 doesn't have an AddProperty(), it was added in VFP 6. You'll probably want to create a grid class with this property and use that, then it won't be a problem.