How to add variable pitch helix data using API?

Iam working on a task that requires addition of variablepitch helix to the existing helix. I tried searching the API's butcouldn't find any. Below is the code available. But it didnt work.

Dim instance As IFeatureManager
Dim Height As Double
Dim Diameter As Double
Dim Pitch As Double
Dim value As Boolean

value = instance.AddVariablePitchHelixSegment(Height, Diameter,Pitch)

Please provide me with some example if you have.

Subbu

SolidworksApi macros