Sure can. In your modules OnPlayerChat event script have it look something like so:
void main()
{
string sMessage = GetPCChatMessage();
object oPC = GetPCChatSpeaker();
int iVolume = GetPCChatVolume();
if (iVolume == TALKVOLUME_SHOUT)
{
SetPCChatVolume(TALKVOLUME_TALK);
SendMessageToPC(oPC, "SHOUTING is not permitted on this server.");
}
}
The message to PC is optional of course. Just an example. Good luck.