Hi, I need some help!!!

I have to edit a movie live. What I mean is the movie will be shown on TV, and I want to use VirtualDub or anything else that can be used to add an effect on the input and directly display it on TV. (I want to add subtitles to it, and I know how to add them) I've got a TV/Capture card and TV out graphics card. I know that this can be done if I capture the video in the computer and then add the effect and then view it on TV, but I want all this to be done directly without capturing the file and saving it on the computer.

Can this be done and how????

Please help!!!