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This is a basic example of how to use the vbapi toolkit for PTC CREO PARAMETRIC (version 9.0.2.0). This also has an example of how LabView does the equivalent of a VB.NET " typecast " to parent and child objects in ActiveX using Variant To Data.
Detailed documentation of the interface is installed with the Creo vba tookit at C:\Program Files\PTC\Creo X.X.X.X\Common Files\vbapi
Looks like will be difficult to draw complex program.
Graphical programming is an interesting way, but for real use need to have predefined blocks. The block must fold all "system" stuff (casting, classes) to simplify user life.