How do I disable a button in an ascx page? I know how to do it on an aspx page with:

```
btnSave.Attributes.Add("onclick", 
  "this.disabled=true;this.value='Please Wait...';needToConfirm=false;" +
  ClientScript.GetPostBackEventReference(btnSave, "").ToString());

```

But the ClientScript function is not present in the ascx page.