Accessing DLL methods with contain mulitple classes using JNA

I am new to accessing DLLs from Java using JNA,so forgive me if this is obvious to everyone! I need to access methods from a class within a DLL(which was written in VB) and cannot do this by just loading the library as I see how to access a class within it I.e. the DLL is called CDrawControl.dll, but the class within the DLL I need to access is DrawCtl. So I need to get an instance of the DrawCtl class. So all in all, how to I reach this method in the DLL using JNA?

I.e. CDrawControl.DrawCtl.SaveFile()

It is probably something very simple I am missing.

public class ReadDLL {
    public interface ChemDrawCtl12 extends Library {
    CDrawControl INSTANCE = (CDrawControl) Native.loadLibrary(
            (Platform.isWindows() ? "CDrawControl" : "CDrawCtl12LinuxPort"),
            CDrawControl.class);

    void DrawCtl.SaveAs(); // this is wrong but shows what I am trying to do!!
}