This my favourite Avenue application area. A good development environment always has ways to talk to other applications. There is no single development environment in the real world. Sooner or later, you'll have to work between languages, glueing them together. If you don't buy that, you've been in school too long.
Avenue has a rich cross application environment with other Micro$oft products. This application interacts with the MS Excel spreadsheet application, both with traditional Avenue and Dialog Designer. The tools are located in the View | Popup document. They do the same thing, but differently. The images illustrate the Dialog Designer process, because it looks more fun. Upon a user defined selection set of fields and records, Dynamic Data Exchange (DDE) is used to open a conversation with Excel.
If there is no Excel app opened, you will be prompted to open the program. Alternatively, one could hardcode the /path/to/the/program/ and use a system call, but this may not be the best choice for a wide range of users, who may not have their programs installed in accordance to your script. What I like to do is store the path at the top of the script, so it can be easily changed when needed. The Excel app opens a blank workbook and writes the selection to the default spreadsheet.
The Dialog Designer environment involves alot more form checking and updating, which could be a bit tedious, but makes for a better GUI. The difference here is that one must be aware of every control's select, update, or click properties, and work out the relationships between controls when chages occur. This is alot like a CGI / Forms application.
This component needs some application configuration to enable the hotlink tool and attach it to your script, with a corresponding field which acts as the passed URL. When the user clicks a region with the hotlink tool, the system's default web browser opens, pointing to the URL. This is especially useful for displaying ancillary / other data about an object without integrating it into the GIS environment. With the cost of GIS integration, this is a great link to existing web-based tables, data and information.