Changing TabIndex in derived form in Windows Application

Hi,
I am having a windows application in which i have one windows form
which derives from one base form.the base form has some controls whose
tabindex is set there in the form.
In my derived form i have some new controls so i want to change the
tabindex of the controls which have been derived from the base form
alongwith the controls of my derived form.
i am trying to set the tabindex property in the derived form in the
form_load function but it's not reflect when i run the application.
what do i need to do?
any help is appreciated.
regards
dipti