Return Month Value

[D2S]

Edit: Attaching workbook

Hi,

I would like to be able to return the month value in the following way, being the current month Value into Month 1:

Sep-17 = 1
Aug-17 = 2
Jul-17 = 3

This means that once we are in October, I want the values to reclassify the following way:

Oct-17 = 1
Sep-17 = 2
Aug-17 = 3
Jul-17 = 4

Thanks in advance,
D2S