I have created a custom dialog for Visual Studio Setup Project using the steps described here
Now I have a combobox in one of my dialogs. I want to populate the comb
I guess you'll have to go beyond the out-of-the-box setup and deployment package and try a third party app.
You may want to look at:
Both are free; they might give you the customization that you need.
I've always found the custom dialogs in visual studio setup projects to be woefully limited and barely functional.
By contrast, I normally create custom actions that display winforms gui's for any remotely difficult tasks during setup. Works really well and you can do just about anything you want by creating a custom action and passing a few parameters across.
In the dayjob we built a collection of common custom actions for tasks like application config and database creation / script execution to get around custom dialog limitations.