Drop downs

I have a acrobat form with a drop down with 3 customer types: Company, NPO, Individual. I also have several drop downs on the same form that might be dependent on my customer type selection. For example, if I select Individual, I want some drop down boxes to have a dash -, because that particular question does not relate to individuals. I manage to do that easy enough. However if I select Individual and I change my mind to select Company instead, the dash - stays in the field. How do I write a code to remove the dash as soon as a change is made from Individual to Company, without having resetting the entire form.