The tab order is set in the order of the way it is written in the HTML form. The only way that I think you can override the order is to force the tab by using the ONBLUR of each control.
Code:
<form>
<input TYPE = "text" NAME = "txtOne" VALUE = "text one" ONBLUR = "txtThree.focus();">
<input TYPE = "text" NAME = "txtTwo" VALUE = "text two">
<input TYPE = "text" NAME = "txtThree" VALUE = "text three">
</form>
The above code in txtOne forces a tab to txtThree. Remove the ONBLUR event and it tabs normally.