You're not getting any responses, because you haven't provided enough
detail.
To Excel, times are numbers (fractions of a day). It doesn't matter how they
are formatted (military, am/pm, etc.).
If your time is in A1, your Low is in A2 and High in A3, you might be
looking for something like:
=if(and(a1>a2,a1<a3),average(b1:b6),"")
If that doesn't help, post back with more information.
Regards,
Fred.