Cell values translated to color gradients: macro needed

Dear Forum,
Hello. I am trying to construct a visual indication of loudness across time. Because I am stuck in excel 2003, I have to figure out how to manipulate colors to the extent that I’d like with VBA. If you look at my attached workbook, you’ll see data, a color legend, and two charts, which are identical except for the series' fills. How to get from “Raw Product” to “End Product” with a macro, by specifying color gradients as values in cells (C3:D45 - start color/end color)? In addition, a preceding IF condition will check for an “R” (in which case there will be no area fill at all).

So far, I have a macro that can change the series into a solid color given cells' values, and I have a macro that can give a series a predetermined gradient already written into the code. I need a macro that will do both at the same time, though.

Any ideas? Thanks.