Time Input Mask to show "5:35pm" ONLY

Hi there,
I am trying to get me date/time field in both the table and form to show
only 0:00pm... 5:35pm as an example.
I have tried a few different input masks the closest one I have got is
0:00\pm, however when I type the time into the field (by only typing 535) it
automatically changes to 5:35AM.
I don't need the AM option at all as all times entered will be a PM time.
Therefore I want it to automatically update as PM.
I also only want to have to type the numbers as indicated before 535. I
don't want the leading zero (05:35pm) and I dont want to have to type the :
nor p/pm.
Hope this makes sense, any help is much appreciated
Rachel