Show custom message in CreateUserWizard ErrorMessage control

Hi,
How can I show a custom error message in CreateUserWizard ErrorMessage Control?
I check some custom rules in CreateUserWizard CreatingUser event and if not passed I want to show an error message in CreateUserWizard ErrorMessage control. I tried to set Text property of ErrorMessage control and set the Visible property to true but didn't work. I use template in CreateUserWizard.
Thank you,
Nima
 
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