How do I start a javascript function from a aspx.cs or aspx.vb program

<script type="text/javascript">
    function function1()
    {
       ...
    }
</script>

Public Class _Default
    Inherits Page

    Protected Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click
         'Execute some code first
         'Then execute the javascript function
         ClientScript.RegisterClientScriptBlock(Me.GetType(), "JavaScript", "JavaScript:function1(); ", True)
    End Sub
End Class