converting mdlArc_createByPoints to vba CreateArcElement2

I am rewriting an mdl application in vba and got stuck when trying to substitute CreateArcElement2 for mdlArc_createByPoints. Is there some math guru out there who can tell me how to calculate the primary radius, secondary radius, sweepangle and get the center point for an arc when you start out with 3 points on the arc? I tried using the original mdl call (see codebelow) but it crashed MicroStation and I couldn't figure out why, so I thought I'd try a vba fucntion instead.

    Dim points(3) As Point3d
   

   Dim arcEl(0 To 250000) As Byte

    status = mdlArc_createByPoints(arcEl(0), ByVal 0, points(0))

Any ideas what I can do?

Thanks,

Stephanie