Regular expression to replace

and

tags

Hi Everybody,
I have an HTML with content some thing like
<div style="margin-left: 40px">a <strong>b </strong><em><strong>c</strong></em></div>
What I want to achieve is
<div style="margin-left: 40px"> to be replaced with &#09;
And </div> with &nbsp;<br> without touching inside contents which are dynamic
I thought this can be achieved using regular expression Regex.Replace but not worked on regular expression.
Can anyone help with proper approach?
Thanks!< ...