Tab to button after field?

[RGould8 at aol.com]

I've got a series of text input fields that I have the user "tabbing  
between", and I'd like to make it so that when the user gets to the last field,  they 
can hit tab, and hilite the SUBMIT button.  Is this possible?   I've got the 
"focus with keyboard" checkbox selected on my submit button, and  I've got the 
"show focus border" turn on as well.  I'm just not succeeding  in getting the 
button to be focusable via the keyboard.
I've also got the icon, hilite icon, visited icon, and armed icon set to  
different icons, just as a test.