ok, i could lookup a predone answer to this at regex sites but... i really need to learn regex, not knowing at least simple expressions will continue to hold me back.

i want to validate a time format, 0:00

where the maximum is
12:00
and the minimum is
0:00

i have a combobox for the AM/PM bit
(this is actually for ASP so no i cant use a timepicker, it doesnt actually relate to asp directly though n figured id get better luck here)

i have tried a few things so far
including
[0-12]:[0-6][0-9]
[0-12]:[00-60]
[00-12]:[00-60]

with no luck... if i havnt been clear already i do not just want you to give me the expression, i would like for someone to explain what needs to be done, and how each expression is written

thanks in advance for any help.