Header Call To Action URL: Open in new tab?

Apologies if this has posted twice - the 'post your question' button kept indicating 'posting' without confirming completion, so I hit refresh to send again.

Hi, great theme, will definitely upgrade to membership once the site is fully configured. However, a quick query re: Appearance>Theme Options>Header tab.

The call to action button notes state: enter your link url for your call to action link (include full path including http://)

This is fine. I entered an external URL to Amazon.co.uk (for our paperback book / ebook) and it works. However, when clicking the button, the redirect does not open in a new browser tab/window. This is not ideal. The Header tab offers no check box option to enable this.

How can the link be configured to open in a new tab, as per other normal linkouts enabled via the WYSISWYG editor on WP pages? We are using WP 3.4.1, BuddyPress install.

Thanks!