//Put this OnEnter
void main()
{

object oPC = GetEnteringObject();

if (!GetIsPC(oPC)) return;

int DoOnce = GetLocalInt(oPC, GetTag(OBJECT_SELF));

if (DoOnce==TRUE) return;

SetLocalInt(oPC, GetTag(OBJECT_SELF), TRUE);
string sMessage = GetLocalString(OBJECT_SELF, "sMessage");
SendMessageToPC(oPC, sMessage);

}