Checking indi values in same window with different scales

[VirtualFM]

Hello math geniuses!

I'm making some experiments and I don't actually need help with coding but with math. I want to check the cross of two indicators. The indicators use the same window and the cross is obvious visually, but I can't find a way to solve the math problem.
The problem is that the indicators use a very different scale. In this example the indicators are CCI which varies between around -200 and around 200 (being -100 and 100 the normal signal values to check) and MACD, which varies in very small values depending on the currency digits and volatility. Not only that, but the visual cue is done "on the spot", in the current time, as if we slide the graph back and forth the crosses will be different.

The idea is express here: https://www.mql5.com/en/blogs/post/712016

As you can see, we should check when the CCI line crosses MACD. Is there a way to determine this through programming, setting a common scale or something?

Thank you for your input.