redirect successful login to previous page, unless triggered by checkout button

The webassist tutorials have made it relatively simple to produce my website - I am almost always able to find an answer by searching the support forum. For my current issue, redirecting a successful login to the page logged in from (unless triggerred by the checkout button), I have not been able to figure it out myself.

Using eCart and Security Assist tutorials, I have a checkout process that triggers login with the cart page, using the checkout rule - if the checkout button is pushed on the cart page, or from any page's Quick Cart, login triggers and, if successful, passes customer through to the checkout page - perfect. However, I added a login button to each page which permits customers to register/login before they have created cart contents and are ready to proceed to checkout ... how can I redirect this successful login back to the page they were on, instead of the checkout page?