checking/unchecking checkboxes.

Hi all:

I have sets of checkboxes like this:
 
checkbox1, checkbox1a, checkbox1b
checkbox2, checkbox2a, checkbox2b
checkbox3, checkbox3a, checkbox3b

When I click Checkbox 1, a popup opens with continue and cancel buttons. I want that when i press continue button on this popup related checkboxes  checkbox1a, checkbox1b should be checked. If I click cancel button,  checkbox1 should be unchecked. How Can I do this ?

Regards,
Asif hameed

 
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