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Well, you could generate such an ID with code such as this:
string evt = "COM";
int id = 100;
DateTime dt = DateTime.Now;
string uniqueID = String.Format("{0}{1:D2}{2:D2}{3}", evt, dt.Day, dt.Month, id);
Notice that you'll need to allow 2 digits for the month if October, November and December are to be catered for.
How unique this is going to be will depend, of course, on how unique the 'id' component is relative to the other components.