From Mladen:

One more experiment : half trend that can be applied to price(s) or any other indicator - the possibility for custom indicators that exists for metatrader 5. That possibility (unfortunately) is not possible for metatrader 4 custom indicators.
On the example bellow, on the main chart it is HT applied multiple times of previous instance of itself + to some randomly attached built in indicators.

PS: when yopu apply any indicator to another indicator, metatrader 5 uses only first buffer of the target indicator. Hence, if your indicator is not providing "significant" values in first buffer the results are not going to be what you expect