A NumericUpDown control is probably a poor choice for this, unless you are just trying to pick an hour between 1 and 12 inclusive, in which case it's trivial - so I suspect that you want something more complicated, such as AM / PM or hour and minutes, and so forth.
If that is the case, why not use a DateTimePicker instead? It allows you to specify the Format as Time, and disable the calendar button to show an up / down button instead.
Just set the properties in teh designer:
Format Time
ShowUpDown true
or
Format Custom
CustomFormat hh:mm
ShowUpDown true
If you aren't interested in seconds.