If I understand your question correctly, you currently use the above code to add a TEXT signature to a user’s mail file signature, is that correct?
If so, what you say now is that you want to add an HTML signature to a user’s mail file instead, correct? The only way I know how to do this, is the way I did it in the past. I sent the users an email explaining what it would do, then I had the button create a local HTML file (using LotusScript) that matched specifically to the user’s needs. Then I pointed their CalendarProfile to the HTML file I just created locally.
Unfortunately, this is how the HTML signatures work. Now, if I have misunderstood what you are trying to do, please explain further and I will see if I can help further.