I am not even sure if the Targeting Computer was able to do that. When I read the books it was always like this: Get the 2 cross hairs to cover each other and turn gold and fire at will. I doubt I would be able to handle two cross hairs with a mouse and keyboard only tho

You could do that in the books, yes. As to how you can do that, some people (other than me) like to use two joysticks. I think there's a thread around here somewhere with someone talking about that. Yep, a quick check shows it's only a couple of threads down from this one. Of course adding the feature would be pretty pointless.