You can use the TabIndex order dialog establish the order of the TabIndex property of the controls that support it, for example, the Push button control. The TabIndex variable of the controls which support it determines how the browser / platform must deal with the control when the user press the TAB key.
You can use the dialog controls to establish the order that you wanted. The TabIndex order is established in the same order than the controls appear in the dialog list, so the first control is the first reacting to the TAB key, the second is the second one, and so on. You can also use the dialog to reset a previously established order, by pressing the dialog Reset button.