problem whith getting value from CreateUserWizard

hi all,
i have CreateUserWizard and its contain 3 steps:
 
the first step is CreateUserStep(Default step) and getting the value from UserName Texbox as follow:
 
TextBox UserNameTextBox =  (TextBox)CreateUserWizard1.CreateUserStep.ContentTemplateContainer.FindControl("UserName");
 
string text= UserNameTextBox.Text;
 
and its work , but in the Next step which name is (UserInfoStep) when i trying to get value from any control i get error like this
 
" Object Reference is not set to null"
 
how i can get value from textbox called (UserCountry) from step called (UserInfoStep)
?
 
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