Fibonacci Trader - Rapid RSI

I need to be pointed in a direct to get help with coding indicators for Fibonacci Trader 4. Im looking to code a simple Rapid RSI indicator in either excel or dll format. As it takes either format.

Rapid RSI is:

RSI = 100-(100*[1-RS])
RS = Sum of X day's up closes / sum of X days down closes

the RSI part of the code is easy. However, as i have limited coding knowledge im finding it hard to code the RS part.

If no one can help with the indicator, could someone point me in the direction of further tutorials on coding for Fibonacci Trader?

This is as far as I have been able to get to and I'm having some issues. Could someone suggest to me what I have been doing wrong?