tab Index is not working properly

Question

Hi,

I have two group box in form each group box have some text boxes and button control.
for ex: 
 groupbox 1 have 3 textbox and 1 button
 groupbox 2 have 3 textbox and 1 button

I have given tabIndex first to text box and then to button


group box 1

Textbox1 - tabindex = 0
Textbox1 - tabindex = 1
Textbox1 - tabindex = 2
button -  tabindex = 6

group box 2
Textbox1 - tabindex = 3
Textbox1 - tabindex = 4
Textbox1 - tabindex = 5
button -  tabindex = 7



Problem is tab Index is not working properly. Afert third text box of groupbox 1 it goes to button of groupbox one.I want tab index like above Please suggest how can I do.

Thanks