Difficulty with converting a desktop app to a web app

I am basically using Xojo to rebuilding another program previously built in Visual Basic 6. My superior wants me to build this as a desktop app, because that is what the VB6 code originally was. After that, we are going to convert the desktop app to a web app. I need to know if this is a reliable plan.

In Xojo, can a desktop app be converted to a web app? What would be the best way to do this?

Make sure you abstract the business logic outside of the windows/containers. If your web app will essentially be the same experience then you can duplicate most of the code. The biggest gotcha is if you do any heavy processing. On the Web version the server will be doing all the work as opposed to the desktop(s).