Adding new button in Postbit

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I would like to add a new button next to the, Edit/Quote, buttons in each post.

Problem?

I can't find the right place to put the code/template info.

I created a new postbit template (which contains the link and image html), and then to eval it I did a

if (ismoderator($thread['forumid'])){
  eval("\$quoteDBlink = \"".gettemplate("postbit_addquote")."\";");
} else {
  $quoteDBlink = " ";
}

$quoteDBlink is then in main postbit template next to where the Edit/Quote buttons are.

basically I only want mods of the forum or admins to be able to see the button.

Thing is the button never shows up. I've tried to add that code to showthread.php in a few places to no avail thus far.

Where can I add this code so that the button shows up in the right place and for the right people.

TIA