Show repainting of 1 buffer of a custom indicator on past bars and on a live chart (mql4)

TLDR: add 1 buffer that displays the historical values of 1 buffer of a custom indicator, 

both historically (as if it ran in real time from left to right of the chart), as in real time

Don't bid if you are in doubt about how to do this.

1) Intro:

When you are not sure if an indicator is repainting or not (changing its past values as new bars arrive), a neat little trick would be in MT4 to open: a 1-minute chart, put your custom indicator on it with your desired settings, and then, open the Navigator window, click on Indicators, click on Trend, then drag the indicator "Moving Average" into the separate window at the bottom of the chart: on top of the custom indicator you want to check for repainting, before releasing the left mouse button. Then when you release that button, in the Moving Average pop-up box, you give in the following settings: Period: 1, Shift: 0, MA method: Simple, Apply to: First Indicator's Data. This will be the most effective on an M1 chart, because it produces the most bars in the shortest amount of time. The SMA(1,"custom indicator") will chart a line that gives a historical snapshot of where the repainting indicator was in the past, on the close of the bar, effectively showing how it repaints.

2) Problem:

I have a custom indicator in a separate window, for which I want to see the "historic repainting", but without having to use the procedure described above in 1). So an extra buffer needs to be added to the mql4 code. When I drop the new indicator on the chart, I want to see how it repainted in the past, for all the bars the initial indicator is calculated on. However, it also needs to work in real time, so as new bars arrive on the chart over time, the new buffer on the required indicator shows where the original repainting indicator was at the close of the bar. 

3) Technical:

It should work on all instruments, all timeframes, all bar types in MT4, not just in the past, but also in real time. 

4) Criterion for success:

The new buffer in the proposed solution should have the same values as the SMA(1) described above in 1). The original indicator (with multiple buffers) works fine, both historically and in real time. Without array-out-of-range issues, and compatible with the latest standards in mql4 for Metatrader 4. 

The buffer in the attached code that needs to be evaluated is called "ExtMapBuffer2": the one with the label: "Bars to previous extreme".