Using CoffeeCup HTML Editor, some kind of script, can I force clients browsers to open in a tab?

If you go to the source code of the HTML Editor, and locate your link, it'll resemble something like this: <A href="(LINK)"> (Desc) </a>, if you want to open this link in a new window every time, you have to add target="_Blank" right after the link, but before the >. This should open the target window in a new tab.

I hope this helps.