According to
this link, it appears that Copperas Cove is on an EDACS Pro-Voice trunked system, so if this is correct, you're pretty much screwed - Pro-Voice systems can not be monitored with a scanner. It looks like infomation on this system has not been updated in nearly a year, but I would still call it reliable.
However, you can visit
here and see what frequencies are being used in Coryell County.
Hope this helps...