>Is there some simple way to hack a VCX to add custom properties to a number of the classes defined there?

I would not hack the vcx as data. Also you would normally add properties to a base class only.

Travers a project with for each loFile in _vfp.Activeproject.Files. Check for files of type classlib (loFile.Type="V"), Use AVCXCLASSES() to get a list of classes of a vcx file (loFile.name). Use ACLASSES() to find ancestors/parent classes of a class.

When you found the root classes

MODIFY class xyz of some.vcx nowait
ASELOBJ(laXYZ)
loXYZ=laXYZ(1)
loXYZ.AddProperty("newproperty")
..

You may previously check if a property already exists with AMEMBERS(). It's all there, you don't need to hack data.

Bye, Olaf.