From that statement alone I don't know what you are trying to do.
If you haven't seen it, you can set the annotation and the timestamp with the set value. There are three set functions on context points:
set(value); //set the value at the timestamp that triggered the script
//set a value at a timestamp. If the "saves historic" is not checked on the scripting data source, this will
// go through the DataPointRT's savePointValue method, which has some logging subtleties
set(value, timestamp);
set(value, timestamp, annotation); //just like previous, but with annotation as well
So a meta point could have a script like,
my.set(p1.value, p1.time, "custom-annotation");
return UNCHANGED;
Which would have the meta point have the same value at the same time as the context point, but with the custom annotation.