trigger on events/tasks to update opportunity

I think I figured it out. Thanks for the code!
Trigger changeopp on Event(after update, after insert) {
    string eid;
    list<opportunity> oplist = new list<opportunity> ();
    list<opportunity> opToUpdate = new list<opportunity> ();
    for (event e: trigger.new) {
    eid= e.whatid;
    if(eid.startsWith('006')) {
    oplist = [select name, stagename from opportunity where id=: eid and (stagename= 'Contacted' or stagename= 'Start - go for it!')];
        }
    }
    for ( opportunity opp: oplist) {
    opp.stagename = 'Appointment scheduled';
    opToUpdate.add(opp);
    }
    update opToUpdate;
}