I'm trying to get a cell highlighted if its value contains the (alphabetic)
value in another cell. I've got a rule in cell C16 of =B5 ="td" and this
correctly highlights when C16 and C5 are both set to 'td'.

But I want it to really to be 'contains' not '=' and then to be able to put
in a string of values 'td, ps, jc' and so on. So C16 could be set to 'JC/PS'
and would go red if C5 contained either 'JC' or 'PS'.