Decklink SDI Graphics Output - Repost - open to bidding

We are developing a windows software that creates animated graphics on screen. We want to be able to send them to the 2 SDI outputs of a Blackmagic Decklink card in the form of a fill+key signals using the alpha channel of the frame. The goal is to overlay our graphics (text, sprites, etc..) on top of a TV studio live image. We need to do it with internal or external sync. We need a class, a control or a dll managing that functionality to include in our VS C# project.