Flutter and Excel VBA are two different technologies used for different purposes, so they don't directly interact with each other. However, you can achieve integration between them using various methods. Here are a few approaches:

1. **File Interchange**:
You can export data from your Flutter app to a file format like CSV or Excel-compatible formats (e.g., XLSX). Once the data is exported, you can use VBA in Excel to read the file and perform further operations.

2. **API Integration**:
If you have a backend server for your Flutter app, you can create APIs to interact with Excel files. Your Flutter app can send data to the server, which can then use VBA or other technologies to manipulate Excel files and send back the results.

3. **Third-Party Libraries**:
There are third-party libraries available for both Flutter and VBA that may offer integration capabilities. For example, you might find a Flutter package that allows communication with Excel through COM (Component Object Model) or other mechanisms.

4. **Web Scraping**:
If your Excel VBA code interacts with web-based resources, you can build a Flutter app that mimics the behavior of a web browser and interacts with the same resources. You can then scrape data from the Flutter app and use it in your VBA code.

5. **Database Integration**:
Store data from your Flutter app in a database, and then have Excel VBA connect to the same database to retrieve and manipulate the data. This approach requires setting up a database server that both your Flutter app and Excel VBA can access.

6. **Direct Integration (Advanced)**:
It's possible to directly interact with Excel from Flutter using platform channels and native code (Java/Objective-C). However, this approach is complex and may not be suitable for all scenarios.

Choose the approach that best fits your requirements and technical capabilities. Remember to consider factors such as security, performance, and maintenance when integrating Flutter with Excel VBA.