dcl_Project_Unload

Hello
Can anyone tell me why this does not work?
Stayed here on the forum and looked in the help wanted but I is not wiser.

(defun c:cadtool_Main_cmdclose_OnClicked (/)
  (dcl_Project_Unload "Cadtool")
)

Try this:

(defun c:cadtool_Main_cmdclose_OnClicked (/)

  (dcl_Project_Unload "Cadtool" T)

)

YES  :D

Thanks