How can I hide certain custom fields in the checko

I'm guessing that it is something to do with the checkout/fields.php file?

For example, I have a custom field named co_carrental it is only relevant to certain customers.

So, I would like that field to show for those customers, but be hidden for the rest. So basically if a variable $car equals 1 then show the field co_carrental and if $car does not equal one then don't.

Is this possible?

okay, I just found this post on "conditional required fields":
www.hikashop.com/en/forum/4-how-to/42933...required-fields.html

That looks like what I want. I'll give it a shot and get back if I need more help.