Adding a custom field to create user

 Hi I am using a custom create user box which also allows you to add roles to the user and works fine, I want to be able to add a custom control to a users account which will assign the user to a lab so if we have 5 labs then when I create a new user I can asign them to a lab or multiple labs
the below shows the difrent roles availible would i be able to add another so it shows the labs in a listbox so the lab can also be chosen, I have a table called Labs with a Lab_id and Name 
 

// Activate event fires when the user hits "next" in the CreateUserWizard
public void AssignUserToRoles_Activate(object sender, EventArgs e) {

// Databind list of roles in the role manager system to a listbox in the wizard
AvailableRoles.DataSource = Roles.GetAllRoles(); ;
AvailableRoles.DataBind();
}

// Deactivate event fires when user hits "next" in the CreateUserWizard
...