textbox not updating

Hi Guys i am trying to update a textbox when the form iInitializes but this does not seem to work i cant understand why. Here is my code:

(setq txt "This is a test")

(defun c:MyCivil3D/Form1#OnInitialize (/)

(dcl-Control-SetText MyCivil3D/Form1/TextBox1 txt)

)

Have you checked all other stuff?
- the dialogue is loaded and active?
- other controls are working fine?
- can you modify the textbox with another command after initializing?
- the textbox-control has all needed events activated?
- ....