Link to anchor tag?

We are looking at using Draw Attention to drive users to more information – not to a separate page, mind you, but to content further down the page where the imagemap lives. We can set the link to an anchor link using the normal format in the URL (full_url/page#anchor/) BUT because we are using a sticky header, we need to provide an offset of about -150 pixels, so we have a CSS fix for that, but there is no way to provide a different class to the URL in DrawAttention to use the extra css … or is that something available in pro?