How to change Transparency of specific edges in a graph plot?

I have a plot, p, with 498 nodes and 6065 edges.

p has a property, EdgeCData, which ranges from 500 to 500000, based on resistence of a transistor - this forms the color data.

p also has a property, EdgeAlpha, which changes the transparency.

I would like to ONLY change the transparency of edges with an EdgeCData > 500, however when I change EdgeAlpha, it changes all the transparencies.

Furthermore, I am using a colormap to represent the values between 500 and 500000, is it possible to maintain transparency on this colormap?

Any idea?

Thanks!