Trading – How to track the best time to sell stocks and buy cryptocurrency?

There are many stocks and mutual funds in my portfolio. I’d like to sell some of these “traditional” investments and buy some cryptocurrencies. But I’m trying to figure out how to calculate when is the best time to do this transfer.

Basically what I want is to view a chart and set an alert like this:

1. When the stock price is high (relative to my fiat currency)
2. When the cryptocurrency price is low (compared to the fiat currency above)

First, what should we do theoretically? Is there a way to construct a chart that simplifies two lines into one line? This is some calculation for two lines that will show a single line with a very high point on the y-axis if the above two conditions are true and a very low point on the y-axis if the above two conditions are not true.

Second, how can I set up an alert to tell me when the chart above has reached some kind of yearly high so I can be notified that “now” is a good time to sell stocks and buy a given cryptocurrency?