Does anyone know if this is possible?:

I sell items that can be engraved (two lines of text) for an additional cost. I'd like to have two attributes: one that allows the customer to enter their names and one that allows them to enter their upcoming wedding date. I'm not sure how to set it up though (see below for sample wording on product page). I can set the first attribute for the names and tell it to add $4.00 to the product price and set the second attribute for the date to be free, but if I do that, they will think the date is always free because it won't have the additional fee beside it. If they fill out the "wedding date" attribute and not the "names" one, they won't be but they won't get anything engraved at all, because there will always be a fee of $4.00 to engrave. I guess what I need is an attribute set, which has a single charge for both of the options combined. Does anyone know if this is possible? (Hopefully I explained it well enough!

Customize your *item* for only $4.00 more!
Names:
Wedding date: