|For the first part of your question, try this:|
This will divide the number of "yes" entries in Column C by [the total number of entries in Column C minus the number of "n/a" entries].
re: "for column D I need exactly the same as above but where yes = 100, no = 0, 2 = 200, 3=300 and 4=400 to create a percentage"
I'm confused. A percentage of what? Based on the results you requested for the first part of your question, you basically wanted the percentage of "yes" entries based on the total all the "yes" and "no" entries. (2 "yes" out of 5 entries is 40%)
For the second part, which of those values (yes, no, 2, 3, or 4) do you want to know the percentage of?
For the last part of your question, look up Conditional Formatting in the Excel help files. It will all be explained there.
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