I want to use Brother label printers to print labels.  How do I declare variables of the right type so I can use their interface (dll) file?  Here's their interface:

b-PAC 3.2 API Reference

This describes the classes, structures, shared objects, and interfaces.

For instance, I need to open a document object then populate some of the text objects on the document with data. 

Here's a C# example (I think)

// Document sample

bpac.IDocument doc = new bpac.Document;
doc.Open("File Path");
// Printer interface acquisition
bpac.IPrinter printer = doc.Printer; ...
// Object collection acquisition
bpac.IObjects objs = doc.Objects; ...
// Object acquisition
bpac.IObject obj = doc.GetObject("Object1");
obj.Text = "Test";
doc.Close();

I understand that I can declare global external functions, but how does this help me declare the different interface objects?

TIA, Tracy