Hi Rudolf,
The path to VI's in a built application is defferent than in the development environment.
First, include the dymanically called VI as a "Dynamic" in the app buildler.
If the VI you want to invoke is in the same folder as the VI calling it, you can take the path of the calling VI, Strip it once, at that will give you the path to the folder where the dynamic VI is.
In the built app, you have to strip the path twice.
There are a number of ways of determining which method to use, when.
If the app is running in the dev environ., the file extension will be ".VI".
In the built it will be ".exe".
There are other methods you could use, this is just one.
I hope this helps,
Ben