How to call different pages on server side confirm ok and cancel

I want to redirect the page on other form when click on ok of confirm and when click on cancel then cancel how i do this.. i use below code but this is not redirect to another page. i want to use the server side confirm not client side

protected void Page_Load(object sender, EventArgs e)
{
    string message1 = "Do you want to Submit?";
    System.Text.StringBuilder sb = new System.Text.StringBuilder();
    sb.Append("return confirm('");
    sb.Append(message1);
    sb.Append("');");
    ClientScript.RegisterOnSubmitStatement(this.GetType(), "alert", sb.ToString());

}
On button click i call

protected void btnMsg_Click(object sender, EventArgs e)
        {





            System.Text.StringBuilder sb = new System.Text.StringBuilder();
            sb.Append("<script type = 'text/javascript'>");
            sb.Append("window.onload=function(){");
            sb.Append("Response.Redirect('WebForm2.aspx'){");
            sb.Append("</script>");
            ClientScript.RegisterClientScriptBlock(this.GetType(), "alert", sb.ToString());

        }
    }
}

I want to redirect on webform 2 on confirm ok button click and on cancel i move to another..but this is not done plz recmond how i redirect this