Add feature to existing envelopes indicator

I have an indicator that displays multiple envelope levels in one, all with different settings.

Currently the indicator only shows the Main levels as per the chart below, we run an upper and a lower envelope at each level always visible on the chart.  I want to add a feature that will add mid levels when the price is between two main levels and then remove that if it moves out of that zone. Please see screenshot for a visual example of what I am looking for.

• IF price is between two of the levels shown below, show a mid envelope line.
• This will be used on live charts and also offfline charts so must be compatible with both.
• Only needs to be calulated on bar close, as thats when showing the mid line matters.
• So if price is between 0.13 and 0.21 envelope level show the 0.17 envelope on the chart.
• Only show the mid level on the chart when the price is between the main levels, once price moves out into another main level pair remove the mid level from the chart and display the new mid level. E.G.

1. Price is between 0.13 and 0.21 so mid level 0.17 is displayed on the chart.
2. Price moves down between 0.21 and 0.34 envelopes.
3. 0.17 mid level is removed from the chart.
4. 0.27 mid level is show on the chart.

Envelope Levels used within indicator.  Between each level is a mid level.