[xwiki-users] How to add a Dialog Box similar to Add New User Dialog using groovy or velocity

Hi All, I want to show a dialog window similar to the one that is shown when you want to add a user. A "Registration" window is shown. I was looking for documentation on how to do that but I couldn't find it. So I used the Modal Box component. But I want to keep the consistency on the look of my xwiki site. Could somebody point me some documentation on how to add a dialog window similar to the one that is shown when you want to add a user? I want to show the dialog window using groovy or velocity code, if possible. Regards, Abel