Adding funds to an existing gift card

Hello to all.

First and foremost: thanks to everyone for beign so kind in answering my questions. I really appreciate your willingness to share your knowledge.

I am having a truly difficult time dealing with adding value to existing gift cards (vouchers).

Microsoft suggests a method where if I have a voucher with, say, a balance of $50 and want to add $30 to it, I manually do the math operation to increase that voucher's balance to $80.

The problem I see with this method is that is an invitation for errors that can only bring record-keeping and/or accounting headaches.

Allow me to present a real-life example of the problem. I have a gift card identified with "W38" ("W" stands for wedding). This belongs to a couple who are doing their wedding registry with us.

As you may have already guessed, the balance of W38 starts at $0. But as friends and family of the couple start coming in, here comes the need to start adding funds to W38.

What we "thought" we should do is just have multiple vouchers with the same number ("W38") (and have the unique serial number option unchecked). But now we face a problem: how do we consolidate all those W38s into one voucher?

Has anybody found another way of doing this?

Thanks.