Margin calculator for media budget

You've had a number of views with no response as of this writing. I suspect that could be because, although I'm sure you are entirely clear on what you are saying, those of us from outside your working environment are having a hard time figuring out what you mean. For instance, you refer to "Fixed Margin" in your opening sentence, but nowhere else in the examples. Yes, you refer to margin fees and presumably there's a relationship between the two, but those margins fees aren't fixed (or if they are, it's in some undefined way). 

And you no doubt understand the significance of adding "a rate card on the top" but that's just jargon from an outsider's point of view.

My suspicion is that the formula you're looking for is going to be very simple; but one needs to understand the situation more clearly to write it.