function insert_var( var_name ){
  	var o_text   = document.getElementById( 'theme_contents' );
	
	// Get caret position
	var s = new Selection( o_text );
	var res = s.create();
	var ca_begin = res.start;
	var ca_end   = res.end;
	var part1    = o_text.value.substr( 0, ca_begin );
	var part2    = o_text.value.substr( ca_end, o_text.value.length - ca_end + 1 );
	var data     = '{' + var_name + '}';
	var data_len = data.length;

	// Insert {template_var}
	o_text.value = part1 + data + part2;
	
	// Set caret position
	if ( document.all ) { // IE
	} else { // FF
		o_text.selectionStart = ca_begin + data_len;
		o_text.selectionEnd   = o_text.selectionStart;
	}
	o_text.focus();
  }

// Cross Browser selectionStart/selectionEnd
// Version 0.1
// Copyright ( c ) 2005 KOSEKI Kengo
// 
// This script is distributed under the MIT licence.
// http://www.opensource.org/licenses/mit-license.php

function Selection( textareaElement ) {
    this.element = textareaElement;
}

Selection.prototype.create = function() {
    if ( document.selection != null && this.element.selectionStart == null ) {
        return this._ieGetSelection();
    } else {
        return this._mozillaGetSelection();
    }
}

Selection.prototype._mozillaGetSelection = function() {
    return { 
        start: this.element.selectionStart, 
        end: this.element.selectionEnd 
    };
}

Selection.prototype._ieGetSelection = function() {
    this.element.focus();

    var range = document.selection.createRange();
    var bookmark = range.getBookmark();

    var contents = this.element.value;
    var originalContents = contents;
    var marker = this._createSelectionMarker();
    while( contents.indexOf( marker ) != -1 ) {
        marker = this._createSelectionMarker();
    }
    var selection = range.text;

    var parent = range.parentElement();
    if ( parent == null || parent.type != "textarea" ) {
        return { start: 0, end: 0 };
    }
    range.text = marker + range.text + marker;
    contents = this.element.value;

    var result = {};
    result.start = contents.indexOf( marker );
    contents = contents.replace( marker, "" );
    result.end = contents.indexOf( marker );

    this.element.value = originalContents;
    range.moveToBookmark( bookmark );
    range.select();

    return result;
}

Selection.prototype._createSelectionMarker = function() {
    return "##SELECTION_MARKER_" + Math.random() + "##";
}