Good afternoon, dear friends.
I created an article form in C # similar to Spring V9, but I do not know how to make the GCPBEA methods coming from the Interop.IGcpBS900.dll dll communicate with the Article form. 
Remembering that I was able to import the dll from spring to Windows form C #
Without forgetting that I have already added the library 
and instantiated the class this way:
using Interop.GcpBE900; GcpBEArtigo Articles = new GcpBEArtigo ();
Good
You can not have ERP to communicate with this form directly. You have two ways to do this, or pass the "BSO" instance through the integration API, but for this you need a license.
In the first case it would be something like that in the .NET project. Create an interface that is ComVisible with a "BSO" property, then in VBA in the company opening event you set that object.
namespace FichaCliente
{
[Guid(Guids.InterfaceId), ComVisible(true)]
public interface IEventos
{
[DispId(1)]
object BSO{ [DispId(1)] set; }
}
}