Regular Expression repalace with Uppercase

[TheVig]

Ok. Not quite there yet, but so close.

So I have things like this:
"Tuesday-Friday 9:00 a.m. to 9:00 p.m."
"Tuesday-Friday 9:00 am to 9:00 pm"
"Tuesday-Friday 9:00 AM to 9:00 PM"

I want it to be:
Tuesday-Friday 9:00AM to 9:00PM

With the callback function it matches the whole thing, when I want to just do submatches where only the "a" and "p" are matched.