I'm just spinning something here and this might be an overly-simplistic approach, but what if you created a column for Running Total Calculation in DAX.

Then add a Result column with a simple logical test, i.e. if Running Total column is greater than 20 show Running Total, else show 0.

Then, on the table visual, set a Conditional Formatting rule on the Text Color to be the same as the background if the value of the DAX column is 0, or less than 20.

Here is a link to good solution for creating the Running Total Column Cumulative (Running) Totals in DAX