I've noticed a difference when it comes to accessing curves using vb (C# in my case).
While trying to create a UDF with a curve reference using C# I can fetch the curve feature:
item = modelOwner.GetItemById((int)EpfcModelItemType.EpfcITEM_CURVE, "nameOfSubItemCurve");
The curve is also visible thru:
features = componentModel.ListFeaturesByType(null, EpfcFeatureType.EpfcFEATTYPE_CURVE);
curves = features.ListSubItems(EpfcModelItemType.EpfcITEM_CURVE);
curve = curves;
In this case the curve reference is an ordinary curve.
But when the curve is created using the "curve from equation" there are no SubItems in the feature object.
Is this a limitation in the VB api?
Note that i'm not including the decleration of the variables item, features, curves, componentModel and modelOwner. Those are defines correctly to represent the current part and feature of the model.