im having trouble working out how to do this

I have two fields of data

Priority / Shift

Shfts are either AM, PM or EVE

Priority will be a number and not Duplicated more then once for each shift. Therefore there could be 1 and AM as well as a 1 and PM

i would like to add an additional priority column like so

New@@Priority@@Shift
2"""""""""""1""""""""""""PM
1"""""""""""1""""""""""""AM
3""""""""""""1""""""""""""EVE
4""""""""""""2""""""""""""EVE
5""""""""""""3""""""""""""EVE

The new column is prioritised by the lowest priority starting with the AM's then PM's then EVE's



If ive not explained this clearly enough and you think you could help please say and ill try and explain it better.


Please help,