I don't know what you are trying to achieve. btn_Click is not a Resumable Sub, declaring it's return as such does not make it so. You may just as well call it directly.
You can also declare a return type for btn_Click if necessary and return a value, the Click event called by the system ignores the return value, though whether Erel would think that this is a good idea I don't know!
If in fact you wanted to wait for the btn_Click event you can do so, but in that case Sub btn_Click will never run as Wait For will swallow the event