Text formatting (bullets) issue with IE7 +

[knowledgenotebook]

Hi,

The following code works for IE7 but not IE8 nor IE9
<iframe id="txt" />
<img onclick="var x =
frames['txt'].document.selection.createRange();x.execCommand('InsertOrderedList');x.select();"
src="icons/list_ordered.gif" style="valign:bottom;width:25;height:
20" />

What would work for IE8 and IE9?

Thanks in advance.