Err raised on validation how can i exit

Question

I have a certain webform that collects user information in my webpage when the user hits the

save button it calls a function save() in my dbEngineClass.

Now when the user enters duplicate data i raise a certain error and handle it in the web page

to display a certain message box but after that i want it to exit the class and not do

anything else

but apparently it will continue the execution of the btnsave.click sub

How can i exit the class or prevent the click method from continuing if an error is raised ?

Here is My Code:This Is the Function That saves the info and raises the event

Public Sub SaveNewCustomer(ByVal Name As String, ByVal Tel1 As String, ByVal Tel2 As String, ByVal Email As String, ByVal Address As String, ByVal Coupon As String, ByVal Location As String, ByVal ParamLangaugeID As String, ByVal UserName As String)
    Dim UserNameID As Integer = GetUserNameID(UserName)

    conn = New SqlConnection(My.Settings.CustomerInfoNayefPc)

    conn.Open()
    cmd = New SqlCommand(String.Format("Insert into tblCustomerInfo (Name,Tel1,Tel2,Email,Address,CouponNo,Location,LangaugeID,UserNameID) values('{0}','{1}','{2}','{3}','{4}','{5}','{6}',{7},{8})", Name, Tel1, Tel2, Email, Address, Coupon, Location, ParamLangaugeID, UserNameID))
    cmd.Connection = conn
    Try
        cmd.ExecuteNonQuery()
    Catch CouponNosqlexc As SqlException
       RaiseEvent DuplicateErr()


    End Try

And here is how i handle it in the web Page

Private Sub MydbEngine_DuplicateErr() Handles MydbEngine.DuplicateErr
    Dim strMsg As String = "Duplicate Value exist"
    Dim lbl As New Label
    lbl.Visible = True
    lbl.Text = "<script language='javascript'>" & Environment.NewLine _
               & "window.alert(" & "'" & strMsg & "'" & ")</script>"
    Page.Controls.Add(lbl)


End Sub


    conn.Close()
End Sub

Now after this handler finishes i need it to exit and do not continue the btnSave.click

handler that calls the SaveNewCustomer() sub since when it continues it clears all the

data and i don't want that