Create an Indicator applied on Heiken Ashi

Dear all,

I need an indicator code which is applied on the Heiken Ashi candles and NOT on the standard chart.

Basically, I need it for a certain custom indicator, but you can deliver a well-written and good documented MQL5 source code for a standard indicator (like RSI) as well. I just need to understand what's required to change the indicator code so that the indicator is applied on the Heiken Ashi candles instead of the standard chart.

If you can do it, you can also use my specific custom indicator so that I do not need to update anything by myself.
Thanks a lot in advance for your application.

Best regards