Forecast Triangle in PowerBI

Hello PowerBI Forum,

I need help creating a forecast triangle in PowerBI, I'm not sure how I should structure the data in excel.
The idea is that we do a monthly forecast for the next 12 months, then when we get the actual result. We are trying to compare to our original result to determine how accurate we are.

Vertical data = actual result

Horizontal data = forecast result

Example- row 1- January - we forecast the next 12 months and February is estimated at 24.

                row 2- the actual the result for February is 23, then we forecast out 11 months