Code:
Set oAsmCompDef = oApp.ActiveDocument.ComponentDefinition
Set oOcc1 = oAsmCompDef.Occurrences.Item(oAsmCompDef.Occurrences.Count - 1)
Set oOcc2 = oAsmCompDef.Occurrences.Item(oAsmCompDef.Occurrences.Count)
Set oPartPlane1 = oOcc1.Definition.WorkPlanes.Item(1)
Set oPartPlane2 = oOcc2.Definition.WorkPlanes.Item(2)
Call oOcc1.CreateGeometryProxy(oPartPlane1, oAsmPlane1)
Call oOcc2.CreateGeometryProxy(oPartPlane2, oAsmPlane2)
Call oAsmCompDef.Constraints.AddFlushConstraint(oAsmPlane1, oAsmPlane2, 0)
Set oPartPlane1 = oOcc1.Definition.WorkPlanes.Item(2)
Set oPartPlane2 = oOcc2.Definition.WorkPlanes.Item(1)
Call oOcc1.CreateGeometryProxy(oPartPlane1, oAsmPlane1)
Call oOcc2.CreateGeometryProxy(oPartPlane2, oAsmPlane2)
Call oAsmCompDef.Constraints.AddMateConstraint(oAsmPlane1, oAsmPlane2, 0)
Set oPartPlane1 = oOcc1.Definition.WorkPlanes.Item(3)
Set oPartPlane2 = oOcc2.Definition.WorkPlanes.Item(3)
Call oOcc1.CreateGeometryProxy(oPartPlane1, oAsmPlane1)
Call oOcc2.CreateGeometryProxy(oPartPlane2, oAsmPlane2)
Call oAsmCompDef.Constraints.AddFlushConstraint(oAsmPlane1, oAsmPlane2, 0)