I would like to create a timetable in Excel with the format in the 24 hour
clock without the colon, which I believe is known as military time. I am
leaving the colon out for a number of reasons, aesthetic and to speed up
entry.

I wish to enter the time, for example, 8:30 am as 0800 and have Excel
interpret it as a time, as these will be graphed, so need to be interpreted
as time, and not plainly a number. At the moment Excel simply shows "800"
when I type 0800.

I have tried formatting all the cells as Custom "hhmm" instead of "hh:mm",
but when I enter the time data, it simply shows as 0000 and clicking on the
cell shows the formula of "dd/mm/yyyy hhmm".

Any ideas?