Custom formatting chart axis

Hi all!
Here I have a graph which contains 60 values (30 days a month, 2 shifts a day). All I want, is custom format. I want the scale show 1D 1N 2D 2N 3D 3N 4D 4N... Number means the day of the month, letter means whether is day shift or night shift. I`ve made a screenshot of this as my workbook weighs a ton. Any ideas?

Thanks in advance folks!