Client events can be created on the server. Here's a very simple example:

 <input type="button" value="do it" onclick="Callback1.callback();" />
        <ComponentArt:CallBack runat="server" ID="Callback1" OnCallback="Callback1_Callback">
                <Content>
                    <asp:Label runat="server" ID="lbl" Text="Default"></asp:Label>
                </Content>
         </ComponentArt:CallBack>

protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack || Callback1.IsCallback)
        {
            string script = "function myFunction() { alert ('before callback'); }";
            ClientScript.RegisterClientScriptBlock(this.GetType(), "mycustomscript", script, true);

            ClientEvent ce = new ClientEvent();
            ce.EventHandler = "myFunction";
            Callback1.ClientEvents.BeforeCallback = ce;
        }
    }

    protected void Callback1_Callback(object sender, ComponentArt.Web.UI.CallBackEventArgs e)
    {
        lbl.Text = "did it";
        lbl.RenderControl(e.Output);
    }