In VB6 You can have Project Groups (similar to solutions in Visual Studio .NET)
Project Groups contain usually two or more VB6 projects and have the extension .vbg
To create a project group open up one project, Click File>Add Project
and add a second project. When you click on save you will be prompted to save the Project Group File.
To specify one project as the startup project right click on the project and select Set as Start Up