Text editors

hi,
I want one more button or any image similar like bold function. When it is clicked it should add the html comment / user defined tag . Ex. If database is hightlighted and if i click on the image/button then it should replace with <!--comment_start-->databse<!--comment_end-->.

I think if this function / option is implemented then it would be visible for all the user/client , teacher , admin. I just want to show this function / option for admin or teacher but for client it should be invisible or inactive.

Is the above this is possible in the moodle system ?. can i get the same thing by configuring with admin section. Or I have to write code for this if yes then what / how should be the procedure etc..?

Please response becuase it is very urgent.

Thanks every body,
Bye