cannot executed commands in Timer_Tick

hi, i build a web application, when i try to use a command in Timer1_Tick that open a new windows:
this.Response.Write("<SCRIPT language=\"javascript\">open('Page.aspx','_blank','top=0,left=0,status=yes,resizable=yes,scrollbars=yes');</script>");
or, a command to introduce massege:
ClientScript.RegisterStartupScript(this.GetType(), "myAlert", "alert('HELLO');", true);
nothing is happened, none of them is executing,  but, when these commands is  located in Page_Load it's works.
i hope that someone has a suggestion for me
...