TabIndex of -1 on aspnetspellbutton does not work

[muzi...@hotmail.com]

I set the tabindex to -1 and it does not apply and the source HTML on the rendered page does not show a tabindex="-1". I do not want to allow tabbing to this button based on the flow of my page. My users do not want to tab to that button. They want to move to the next input on the next line below in my form.