Hi,
Like this way, which ever textbox you want to apply the script u can do it.
In Addition to this, from the whole bunch of properties, you can add/delete any feature this way.
tinyMCE.init({
mode: "specific_textareas",
editor_selector: "mceEditor",
theme: "advanced",
//tinyMCE.activeEditor.controlManager.get('disable_save').setDisabled(true),
plugins: "safari,spellchecker,pagebreak,layer,table,save,advhr,advimage,advlink,emotions,iespell,inlinepopups,insertdatetime,preview,media,searchreplace,print,contextmenu,paste,directionality,fullscreen,noneditable,visualchars,nonbreaking,xhtmlxtras,template,imagemanager,filemanager",
theme_advanced_buttons1: "newdocument,|,bold,italic,underline,strikethrough,|,justifyleft,justifycenter,justifyright,justifyfull,|,formatselect,fontselect,fontsizeselect",
theme_advanced_buttons2: "cut,copy,paste,pastetext,pasteword,|,search,replace,|,bullist,numlist,|,outdent,indent,blockquote,|,undo,redo,|,link,unlink,anchor,image,cleanup,code,|,insertdate,inserttime,preview,|,forecolor,backcolor",
theme_advanced_buttons3: "tablecontrols,|,hr,removeformat,visualaid,|,sub,sup,|,charmap,emotions,iespell,advhr,|,print,|,ltr,rtl,|,fullscreen",
theme_advanced_buttons4: "insertlayer,moveforward,movebackward,absolute,|,styleprops,spellchecker,|,cite,abbr,acronym,del,ins,attribs,|,visualchars,nonbreaking,template,blockquote,pagebreak,|,insertfile,insertimage",
theme_advanced_toolbar_location: "top",
theme_advanced_toolbar_align: "left",
theme_advanced_statusbar_location: "bottom",
theme_advanced_resizing: false,
template_external_list_url: "js/template_list.js",
external_link_list_url: "js/link_list.js",
external_image_list_url: "js/image_list.js",
media_external_list_url: "js/media_list.js"
});
<asp:TextBox ID="txtBody" runat="server" style="height: 420px; width: 85%" CssClass="mceEditor" TextMode="MultiLine">
</asp:TextBox>
