how to hide error message after validating

i have a contact form several input box
let's say textbox 1
here on validating event i have written this code
Private Sub TextBox1_Validating(ByVal sender As System.Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles txtuserName.Validating
If (String.IsNullOrEmpty(txtuserName.Text)) Then
ContactFormErrorProvider.SetError(txtuserName, "Enter Your Name!")
Else
here what i hve to write for?????????????????????????????????????if user enter something in this box
End If