Open Staad General Prismatic Member Properties (E)

Hi-

I am using OpenSTAAD (through VBA) to generate a STAAD model and I need to use a general prismatic member. I am able to create the member but I am having trouble assigning "steel" properties to the member. I tried using the commands:

Dim objOpenSTAAD As Object

 Set objOpenSTAAD = GetObject(, "StaadPro.OpenSTAAD")
 Set objSTAADResults = CreateObject("OpenSTAAD.Output.1")

*then I add nodes, and beams, create the prismatic member*

objOpenSTAAD.AssignConstantsToBeam nBeamNo, dE, dDensity, dAlpha, dPoisson

but I am getting an error for the last line

"object doesn't support this property or method"

I have tried to set the material ID to steel, but that only seems to work for beam shapes out of one of the tables (objOpenSTAAD.Property.SetMaterialID 0)

Any help would be greatly appreciated.

Thanks!