To be honest I've had several request to make my indicators MTF, this is something I still need to change on my price calculation function, as OHLC data will no longer be retrieved from the OnCalculate function. Instead one will use the built-in "iopen; ihigh; ilow; iclose; ibarshift; itime" functions of mql5.
This is not very high-up on my list of things to do, currently. But I'll get to it eventually. Once done all my indicators will be MTF. If you are looking for a standard Heikin Ashi indicator, MT5 comes standard with this under the examples folder.
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All comments, criticism, advise or general ideas are more than welcome. In fact its crucial to have a continues learning / developing mechanism not just for me but all fellow market enthusiasts.