Issues using <TAB> key to activate a layer

I am creating a simulation of a program that uses only keystrokes to navigate it's menu structure and screens and it never uses the mouse. I'm running into an issue for which I'm unable to find a cure. Internet searches and searching on this site have revealed some stuff, but not the full cure.

To navigate screens, the learner uses the up and down arrows. Once they have selected a screen with information that can be modified, some of those elements may have popup menus with predefined choices. An example would be selecting "Overnight", "Regular Mail", "Fax", or "Email" as a delivery method for documents. The  arrow keys move from field to field (Name, Address, Delivery Method, etc) and to activate that menu, the program requires the use of the <TAB> key to show the predefined choices. I put these popup menus within layers that are shown when you press the <TAB> key.

And it's the use of the <TAB> key that is causing the issue. The first issue was that a yellow rectangle would show up in the upper left of the published version. Odd, but not a huge deal. Until you needed to tab a second time for another field choice. Then the image would dim and an oval "Back to Top" button would show up in the bottom right corner. Researched and turned that off. Then "Resources" would activate instead. Researched and turned that off too. Then a new issue - Google Chrome, the preferred browser for the company, also recognizes the <TAB> in addition to Storyline recognizing it.

Storyline will show the menu layer, but then focus moves off of the published page and an option is highlighted up near the browser's web address bar (image of that is an attachment to this message.) The only way to get focus back to the page content is use either Shift-Tab or the mouse to click back to the content, neither of which is a natural thing that a learner should have to do within this program.

Is there a way to stop this from happening? Can I get Storyline to do the shift-tab once a tab has been used? I can't find anything on stopping the browser from seeing this...

<Edit> This is in Storyline 3.