First Time SELECT CASE Statement User

Hi, I have created a login page (webform1) that enables me to enter my user number and password and if correct it re-directs to webform 2 where all data related to the usernumber that was entered in the login page, appears.  Now I want to be able to set different re-direct pages dependant upon different users as some may require more privileges then others. As for my query I have 2 types of users: staff and managers. I want to set the login page so that if staff logins in it goes webform 3 and if manager logins in it goes webform 4. My table in the Sql database is called Users & the fields are: unumber(pk), pwd, userRole, forename, surname.
  I have been advised to use CASE statements, yet I do not know how to use them. Below
 have left my code of a simple login without the userRole validation. Please help! Sub cmdLogin_ServerClick  
        If ValidateUser(txtUserNumber.Value, txtUserPass.Value) Then
            Dim tkt As FormsAuthenticationTicket
     
      Dim cookiestr As String
            Dim ck As HttpCookie 
            tkt = New FormsAuthenticationTicket(1, txtUserNumber.Value, DateTime.Now(), _
      DateTime.Now.AddMinutes(30), chkPersistCookie.Checked, "your custom data")
            cookiestr = FormsAuthentication.Encrypt(tkt)
            ck = New HttpCookie(FormsAuthentication.FormsCookieName(), cookiestr)
            If (chkPersistCookie.Checked) Then ck.Expires = tkt.Expiration
            ck.Path = FormsAuthentication.FormsCookiePath()
            Response.Cookies.Add(ck) 
            Dim strRedirect As String
            strRedirect = Request("ReturnURL")
            If strRedirect <> "" Then
                Response.Redirect(strRedirect, True)
            Else
      
         strRedirect = "webform1.aspx"
                Response.Redirect(strRedirect, True)
            End If
        Else
            Response.Redirect("webform3.aspx", True)
        End If 
    End Sub