This should work:
fadeDur = .5;
m = marker;
n = 0;
val = value;
if (m.numKeys == 1){
t1 = m.key(1).time;
val = ease(time,t1,t1+fadeDur,0,value);
}else if (m.numKeys > 1){
t1 = m.key(1).time;
t2 = m.key(2).time;
if (time < t1 + fadeDur){
val = ease(time,t1,t1+fadeDur,0,value);
}else{
val = ease(time,t2-fadeDur,t2,value,0);
}
}