Edit control based on client side message box choice

I have a dropdownlist and was wondering that if after a selection is made, would it be possible to have a message box appear with yes/no values. if yes is clicked a textbox value is 1 if no is clicked the textbox gets a 0.  Then, a code is run, the code has a slight variation if the yes was click or the no was clicked.
 
Thanks.
 -Matt

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