I need to create a warning when specific values sequences are input from a
drop down menu. My example:

I have 31 columns (days in month) and have 25 rows (peoples names) from the
drop down box I have the following values-These are shift designations
(V1,V2,V3,V4, SV1,SV2,SV3,SV4, A1,A2,A3,A4,N,R1,R2,R3,DB,C).

If the selections in cell between B1:AF25 are either SV 1-4 or A 1-4 I want
a warning to appear IF a value of V 1-4, R 1-3, DB or C are attempted to be
put in the immediately following cell.

Example: Cell B3 has A-4 and in cel C3 they attempt to put N, then it
should give a warning "This is not a recommended shift sequence".

Your assistance would be greatly appreciated.