ActionScript 3.0 :: Load External Swf And Set As Typed Variable?

So I have ClassA and ClassB. Each of these is the document class of two different FLAs. In ClassA I want to load a SWF and set it to a variable of type ClassB. The problem is that ClassB uses a ComboBox, so when I try to type the varialbe, then ClassA complains that it can't fine the definition for ComboBox. If I add the ComboBox component to the library of ClassA it works just fine. But that kind of defeats the puprose of me creating the seperate SWFs in the first place... smaller file sizes. So here is basic code of what I'm trying to do.

Code:
package
{
import ClassB;
public class ClassA extends Sprite

[Code].....

If I don't try to type the variable "swf" to ClassB then it works absolutely fine. But I want to have it typed so that I can then use intellisense/code completion in my IDE and not have to worry about the compiler telling em that functions don't exist on ClassB when I try to use them and such.

how to accomplish this? I have found that I can have ClassB implement an Interface and then set the swf to type IClassB... but I really don't want to have to do that because that means for all swfs I want to load I will have to create another Interface and prototype out all the functions. That just seems extremely tedious as this project will get very big.