Yes, yet another Excel query. Sorry but ages on Google still hasn't found an answer.

I'm using Data Validation to create a drop-down list that has the options "Yes" "No" and time in increments of 15 minutes, starting from 16:00 until 15:45. This refers to a list in a sheet Names!A2:A99 where A2="Yes", A3="No", A4=16:00, A5=16:15 etc

Of course Excel really records times as a fraction of a day. The time 16:00 gets shown in the formula bar on the top as 16:00:00
When I use the drop-down box in Data Validation if I select say 18:00 then it works, but if I type in 18:00 it rejects it as an invalid option. If I type in 1 then it recognises that (despite 1 not being on what I want the list to be) and displays it as 00:00 with the top formula line showing 01/01/1900 00:00:00

I can get the times to work using Data Validation->Time instead of ComboBox, but I want either limited words or a time to be allowed. Can't seem to get them to work together.

Any suggestions?